I was trying to set up an analysis that really wasn’t only about the United States. I was trying to understand the ways in which the United States is similar to or different from other countries that industrialized in roughly the same time period, the late 1800s and the early 1900s. A lot of the same things that were happening in the industrial centers of Europe, with the rise of the labor movement and the mobilization of workers, were happening in the United States as well. All of this happened a bit later in the United States than in Europe, but there were many similarities. The United States ended up going in a very different direction, and I wanted to understand the roots of how that happened.

It turns out that whether a country adopted proportional representation or stayed with a system of winner-take-all districts mattered a lot for working-class political mobilization. And I think understanding that story and laying out the history of why the United States ended up the way it did is important for understanding what is happening today.

Economic geography developed in relatively similar ways in the early part of the twentieth century in lots of places that were industrializing. The parties that we think of today as left parties were largely formed and organized around the interests of workers.

Those workers were usually quite concentrated in a space, because of the way the agglomeration economies associated with industrialization led to a concentration of production and, as a result, a concentration of industrial workers. That in turn led to a concentration of working-class housing, and it shaped the way the built environment was structured in lots of different countries. And that led to a long legacy of geographic concentration of voters for the parties of the Left.

So left voters end up much more concentrated in space than voters for parties of the Right. And that really matters when you start drawing winner-take-all districts as we do in the United States and the UK and a variety of other countries that were colonized by the British.

These winner-take-all districts are often relatively small. When we start drawing districts in a context where the main social support base of the Left is highly concentrated, it leads to a number of outcomes that I trace out in the book.

One of them is difficulty in transforming votes to seats. Another is a problem with fracturing on the Left, and coordination dilemmas at the level of districts, of the kind that we just saw in the most recent British election. The Left ends up either divided or underrepresented, or some combination of those two.

I don’t mean to discount the importance of gerrymandering. The way districts are drawn matters a lot. In fact, the book highlights the role of gerrymandering and tries to identify the settings in which it is most important. I also don’t discount the role of legislation that affects access to the ballot. But these efforts are not the entire story.

In fact, the urban concentration of left voters actually structures not only the mechanics of gerrymandering but also of registration and turnout. Policies that might make it more difficult for people to maintain their registration and vote are especially relevant for people who change addresses frequently, and these are typically urban residents.

The point is not that gerrymandering and ballot access are unimportant, but that political geography is central to understanding how these things matter. When it comes to gerrymandering, in some US states, if we run a lot of computer simulations and draw a large number of reasonable redistricting plans that would seem compact, nonpartisan, and “fair” to most people, we’ll still end up with a concentration of Democrats in cities, which will lead to their underrepresentation in the legislature.

But there are some other states where the emergence and growth of cities have unfolded differently, and Democrats are less concentrated at the relevant scale for redistricting. In those states, if we see a real asymmetry between votes and seats, we can point the finger at intentional gerrymandering. Understanding these geographic patterns only helps us better understand the role of gerrymandering.

In a state like Pennsylvania, where Democrats are quite clustered in cities, it would take some intentional effort to draw districts that achieve fair representation. Yet we can still see that the Pennsylvania congressional districts in the last round of redistricting were drawn in a way that pushed the Republican seat share even further than what it would have been in the absence of those efforts. The Pennsylvania courts were convinced of this when they struck down the Pennsylvania congressional map.

There’s been a long-standing effort to try to find ways of convincing the Supreme Court that it is possible to quantify gerrymandering, and the Court has been skeptical about that. Efforts have focused on the construction of a single statewide indicator of gerrymandering, but none of those efforts took geography into account.

A problem with a lot of what people had been doing in this space is that it was easy to demonstrate that the translation of votes to seats was quite unfavorable to the Democrats. But it was unclear whether that was an effort of legislators who were drawing districts in strategic ways, or if this was an outcome we would have expected even from a party-blind redistricting process, simply because of the asymmetric clustering of Democrats. The courts were quite aware of this problem, and it informed their skepticism.

In my initial work on political geography, I viewed gerrymandering as a kind of a nuisance — something that got in the way of my efforts to isolate the role of political geography in shaping representation. With some collaborators, we started doing a lot of computer simulations of redistricting in different states, and we were able to show that it was often the case that these simulations ended up producing districts that were surprisingly bad for the Democrats.

But we could also see that in cases where the actual enacted districts had been drawn by Republican legislatures, the partisanship of those districts was in some cases completely outside the range of the simulations that we did. We also noticed that in some instances where Democrats drew the districts, they were able to do a bit better than in the neutral redistricting plans.

So we started using that observation as a way to demonstrate to the courts that it’s possible to disentangle geography and intentional gerrymandering. We first used this approach in a lawsuit in Florida. Subsequently, there has been an explosion of this type of research. We now have a community of collaborators among mathematicians and computer scientists and others who are trying to come up with better and more efficient ways to draw thousands — even millions — of alternative plans, altering various parameters, to see whether enacted plans end up looking like outliers relative to large samples of neutral plans. While the Supreme Court has thrown up its hands, this approach has been useful in state court. It has now been used in state court in Florida, North Carolina, and Pennsylvania, and it has led to gerrymandered plans being thrown out.

There are lots of reasons for that. My story starts in the era of early industrialization. Pennsylvania is a good example of an early-industrializing state where contemporary Democrats are concentrated in nineteenth-century industrial centers.

There are other early-industrializing states like Massachusetts and Connecticut where it’s harder to see some of the effects I talk about, because the overall Democratic vote share is so high. Even exurban and rural Massachusetts voters typically vote for Democrats. Pennsylvania, on the other hand, is frequently a swing state.

I also think a comparison of western Pennsylvania and eastern Pennsylvania is a really useful one. The Democrats’ problem is especially pronounced in western Pennsylvania, where almost all of their support nowadays is concentrated in Pittsburgh. The eastern part of the state is a bit more complex and interesting because of smaller industrial agglomerations outside of Philadelphia, and the fact that the Philadelphia suburbs are trending Democratic in recent years.

Yes, the list goes on. Easton, Bethlehem, Allentown — all these places are strongly Democratic. Many of these places experienced a relatively large swing toward the Republicans in the 2016 election, but the urban core of those cities is still very Democratic. And on a smaller scale, they show this same relationship we see in other places, which is that the city center, somewhere right around their City Hall, is overwhelmingly Democratic — something on the order of 75 or 80 percent — and then as one moves out into the inner-ring suburbs and through the periphery into the rural areas, there’s an increase in Republican vote share. That’s the pattern we see in all kinds of different cities.

This has been a long-standing question. It’s been a problem for labor parties in Britain and Australia, for example, since the early twentieth century. Literature on this in the 1950s and 1960s pointed out that labor parties suffered from this problem, which of course leads to the question of why labor parties don’t, as soon as they get into power, change the rules.

The answer to that question has a lot to do with the self-interest of the elites in those parties, who are concerned about what would happen under a system of proportional representation, which would very likely lead to a fragmentation of the Left. If they move too far to the right, they’re fending off challenges from far-left parties. If they move too far to the left, they get challengers from the center, and as politics becomes more multidimensional and we get the emergence of issues like the environment, Green parties are always lurking and potentially threatening them.

So elites from the mainstream parties are often very worried that a shift to proportional representation might lead to a fragmentation on the Left, and with good reason. It can be in their self-interest to maintain the majoritarian system — and especially when they win, actors in politics tend to like the rules under which they were victorious.

We saw that with Justin Trudeau in Canada, who ran in 2015 on a platform in which he was rather explicit about his claim that if the Liberals won the election, it would be the last one held under the majoritarian electoral system. But when it won under those rules, the party changed its platform and is now committed to maintaining the existing system.

Exactly, and then the two parties’ positions about electoral reform switched almost immediately. Labour was demanding proportional representation, as was the case for labor parties in many other countries. But once they swept the Liberals aside and thought they could be the dominant party of the Left, well, suddenly their incentives changed. The Liberals became the champions of proportional representation, and to this day, the Liberal Democrats and other insurgent parties on the left side of the political spectrum are the champions of proportional representation. That’s certainly true for the New Democratic Party and the Greens in Canada, and so forth.

There are ways in which that election does seem like a classic case of much of what I’m talking about, but there is another aspect of that election that is still very hard to grapple with. That is Brexit, which loomed so large for many voters. It’s a little too early to conclude that this is a realignment election because of the shift of some of the old industrial areas from Labour to the Conservatives. It’s possible that it was a short-term vote that really was about “getting Brexit done.” So there are some questions about the future of British political geography left unresolved.

But in general, the observation that fits nicely with the analysis in the book is that the mainstream party of the Left has a difficult task: it must deviate from the ideological preferences of its urban base in order to win the median district.

It’s important to point out that the median district is what determines whether you control Parliament or not. The ideological distance between your core base of support and the pivotal swing constituencies, which in Britain and the United States are often suburban, can be quite large. If the urban core supporters drive the platform, it is possible to end up with a platform that makes it difficult to win those places. And this creates fragmentation on the Left, such that the Lib Dems and Labour end up unable to coordinate and their voters end up splitting the vote.

So when you look at the nationwide vote share and start adding up votes for the various parties, the parties that one might classify, in the current British ideological space, as parties of the Left actually received more votes than the Conservatives. But again, they were fragmented across various parties, and the Conservatives knew going in that in order to form a large parliamentary majority, all they needed was a vote share in the low 40 percent range. And that’s an interesting scenario, when the right side of the political spectrum is unified and the left side is fragmented.

I think that’s not a bad way to describe what’s happening. It’s complicated by Brexit and the multidimensional nature of these issues. But the votes of the Right were more coordinated on one party, and the ability of Conservatives to squeeze out the Brexit Party was an important part of how that was achieved. But the Left was unable to achieve that, of course. With the Scottish National Party, the mainstream party of the Left now in much of Scotland, it ends up with a rather intense fragmentation that makes it very hard to even imagine what the next step might be for consolidation on the Left.

You’re right, the decline of organized labor doesn’t get that much attention in the book. But it is there in the background, and it’s understood that this is an important part of the transformation of the Left.

All the difficulties we’ve just been talking about in selecting a platform and weaving together very diverse constituencies, the decline of labor is a part of that. And the decline of private-sector unions relative to public-sector unions in particular has been important. Public-sector unions still play a relatively important role in the United States and elsewhere. This adds another wrinkle to some of the difficulties the Democrats might face in places where they are trying to please some of their core constituents who are members of public-sector unions. Workers who have not been members of labor unions for a generation now might see the Democrats as catering to public-sector unions and producing nice pensions for local public-sector workers and not doing so much for them, because they just have no connection to the labor unions to which their parents belonged.

I don’t have a clear sense of whether that’s true or not. It’s a difficult gap to bridge. It’s difficult to be the party of San Francisco at the same time that you’re trying to be the party of Scranton, but I don’t think there’s evidence that it’s impossible. I do think all of this becomes a bit easier in a multiparty system, where different parts of the Left can appeal to different constituencies.

We’ve seen this happen in continental Europe, where the Green parties are really the city-center parties of the Left now, and the social democratic parties are still trying to focus on the industrial workers and, in some cases, new migrants. But they have to stretch themselves far less than a mainstream party of the Left in a place like the United States, which probably does at the current moment have to be a party of both Silicon Valley and postindustrial towns. Unless there’s some really major realignment, that’s currently what the Left is faced with.

There are conditions under which that coalition can work. The New Labour period in Britain is an example of that. From the perspective of some folks on the Left, that’s not a good example of something that worked because it was so centrist. But this is the underlying tension. The majoritarian system forces the party of the Left, if it wants to win, to do what Tony Blair did and try to appeal to those suburban and middle-class constituents.

The electoral institutions don’t provide much of a way out of that, but in the United States, it’s a bit more complex than even in Britain because we have multiple levels of competition. We do have statewide races in which it might be possible to, especially in a very urban state that has enough urban voters, not worry about the median voter in the median district and just try to win the statewide Senate or gubernatorial election or electoral votes with an unabashedly urban platform. But that can have a negative impact on your ability to win those pivotal legislative seats. So there’s a tension between strategies based on the median voter, and strategies based on the median district, that is especially strong in the United States.

That’s a great question. Regarding the first part of your question, I’d give a solid yes. There is something unique and quirky about Vermont. It’s something that lots of people who spend time there appreciate. It’s a very unusual state in a number of ways. One of the ways in which it’s unusual is true of Bernie Sanders himself — many of the residents of Vermont were not born there. I think this is an important distinction that matters in a lot of places. Vermont is a state that has seen a lot of in-migration, a lot of it from other parts of the urban Northeast. It’s one of those places, also like western Massachusetts, where even a lot of rural residents are relatively more liberal.

There are parts of the state that are still quite conservative, and they typically vote for Republicans, but your question is about whether an individual with the right characteristics can bridge that urban-rural gap. There’s evidence that Democrats have been able to do that, of course, in places like Montana and elsewhere. It can still be done.

It’s important to note that even though the correlation between presidential voting and voting in down-ballot races is very high, it varies a great deal from one state to another. Just to look at a couple of good examples, Amy Klobuchar in Minnesota and Sherrod Brown in Ohio win big majorities in areas that voted overwhelmingly for Trump. Even in 2016 in Pennsylvania, the geography of support for the Democratic candidates in the presidential and US Senate races was surprisingly different.

So the American voter can be a little more flexible and unpredictable than we sometimes imagine. Gubernatorial races are probably the best examples of this. We see Democrats able to win in places like Kansas and Kentucky. Of course, in Vermont, one of the fascinating things is that ideologically flexible Republicans have been very successful in Vermont gubernatorial elections.

That’s a long-winded way of saying that lots of different strategies are possible, and the one that you lay out seems plausible, under the right circumstances. But at the same time, the urban-rural division is quite stark, and it’s probably not going away anytime soon.

There are a lot of people working on this, and their focus has been on starting local and then trying to demonstrate success and use some of the experimental capacity that US federalism provides us with. There’s nothing in the Constitution that prevents a state from adopting a different set of electoral institutions at the state level. And, of course, lots of US cities are already experimenting with ranked-choice voting and other electoral rules, and there’s a long history of this type of experimentation at the municipal level. One can imagine some state experimenting with some form of proportional representation, perhaps in response to a referendum, so my guess would be the most likely place to see electoral reform would be in one of the western states that has a referendum process.

I don’t expect to see either major party, or elites within these parties, pushing for this. For instance, if we look at New Zealand, their adoption of proportional representation was pushed by independent voter groups, not by the elites in the major parties. We saw something like that in Michigan regarding redistricting reform. You can imagine a group of people pushing for electoral reform in a similar way.

It’s possible for electoral reform to be viewed not as some kind of a project of the Left. There are people on the Right as well who might find that they actually benefit from a more diverse set of choices. All social and economic issues are bundled into these two Democratic and Republican packages, which are very diverse and heterogeneous. But there are lots of Americans whose views just don’t fit perfectly with either party, and plenty of those people are on the Right.

You can imagine electoral reform being kind of like redistricting reform, which can be of interest to people on all sides of the political spectrum. Elites are another matter, but voters are much more open-minded about these things.

I’ve thought about that possibility, and it leads to an interesting question: Why don’t we see more insurgents running under some other label and challenging the Democrats in some of these districts? Maybe some of the answer has to do with the minutiae of ballot access laws and things like that, but I think the bigger-picture story is the presidential system in the United States and the lack of the type of party discipline you often get in a parliamentary system.

That means the Democratic Party really can be many different things to different people, and you can have people who run in some of the most progressive districts as democratic socialists, but the “D” is still next to their name, and they are still in Congress as a Democrat.

The very flexibility of the US party labels, I think, makes it so that it’s not really necessary to start a new party and start running in these districts under some other label. The same kind of individuals who might be interested in doing so can just run in the Democratic primary and try from within to change the brand of the Democratic Party. That’s what has been happening with the Squad and some of the other recent Democratic members of the legislature.

And they have received a great deal of attention, which changes the reputation of the Democratic Party in ways that might not be so helpful for the party in suburban constituencies. In a parliamentary system, it’s easier to see why Greens or socialists might organize under a separate party label and try to squeeze out more moderate incumbents in progressive urban districts, but in the United States, the incentives for insurgents are to work within the existing parties.