New York magazine’s Eric Levitz — probably the sharpest liberal political commentator writing today — has a few bones to pick with Jacobin writers on the subject of Bernie Sanders versus Elizabeth Warren.

The case for Warren as a force for progressivism, Levitz says, is stronger than we’ve allowed. Whatever differences exist between the two candidates will probably end up moot if their policies ever reach the floor of Congress anyway. Moreover, Levitz questions our conviction that Bernie Sanders has the potential to transform American politics in any real way — at least any more than Warren does. Given the country’s legislative stasis and its conservatizing political institutions, he argues, such optimism about any politician is ill-advised.

None of these points is completely wrong, and yet there’s something perverse about this two-and-a-half-cheers-for-Warren case. Somehow, the very fact that Sanders’s post-2016 ascent triggered a historically unprecedented leftward lurch in Democratic Party discourse — a development for which Elizabeth Warren’s rise is Exhibit A — is used to argue that Bernie Sanders has no particular monopoly on the ability to push American politics leftward.

According to Levitz, since Sanders has already “persuaded many 2020 Democratic hopefuls to stop worrying and learn to love social democracy,” the Vermont senator must now be dispensable. This is like saying that since there’s never been a break-in at Fort Knox, there must be no need for all those armed guards.

Yet even as Levitz sees Sanders’s mission as all but accomplished, he also wants to argue that the socialist insurgent has accomplished very little. “Sanders has had a national platform for three years now,” Levitz writes. “He has built up an independent organization and traveled the country proselytizing for class struggle. And none of it has been sufficient for his acolytes to dominate Democratic primaries, or to win him a broader base of support for his 2020 run than he had in 2016, or even to keep his approval rating from slipping underwater.”

It’s true that Sanders has not decisively conquered the American political system for socialism in the space of three years. Socialism is seldom built in a day. Between its first and second electoral outings, the British Labour Party went from 1.8 percent of the vote in 1900 to 5.7 percent in 1906; the German Social Democratic Party from 3.2 percent in 1871 to 6.8 percent in 1874; the French Workers’ Party (whose first election manifesto was co-written by Karl Marx) from 0.4 percent in 1881 to . . . 0.4 percent in 1885. All three of these parties, in some form, went on to transform their countries’ political landscapes — just not in three years.

However, a startling indication of how much Sanders has already changed US politics was recently reported by Martin Wattenberg, a political scientist at the University of California Irvine. Every four years since 1956, the American National Election Studies (ANES) has asked voters to describe, in their own words, what they like or dislike about the two parties. It was on the basis of these interviews that the political scientist Philip Converse reached his famous verdict in 1964 that ordinary Americans are, broadly speaking, “innocent of ideology” — that they don’t think in ideological terms.

Political scientists have generally accepted that judgment ever since, along with a corollary notion, advanced in 1967 by the politics scholars Lloyd Free and Hadley Cantril: that Americans tend, on the whole, to be “operationally liberal” (favoring specific liberal policies like Social Security and Medicare) but “philosophically conservative” (rejecting broad expressions of left-wing ideas).

In a widely noted 2016 book, the political scientists Matthew Grossmann and David A. Hopkins elaborated on this idea, showing that American public opinion is “asymmetric”: while Republican voters embrace broad conservative ideology, rank-and-file Democrats avoid abstract ideas, thinking mainly in terms of which particular social groups will be helped or harmed by each party’s policies.

In the long run, Grossmann argues, Democrats “suffer from not forthrightly making ideological arguments”; “partially as a result, [the] public maintains conservative predispositions.”

But Wattenberg’s detailed analysis of the ANES voter interview transcripts has led him to conclude that in 2016 something fundamental changed in American public opinion:

Past research has shown that Republicans are substantially more likely to be ideologues whereas Democrats are much more inclined to conceptualize politics in terms of group benefits. This pattern was quite evident in the 2008 and 2012 American National Election Study (ANES) responses that I personally coded.

However, two developments occurred in 2016 that dramatically reshaped the partisan nature of belief systems. First, the Bernie Sanders wing of the Democratic Party evidenced a great deal of ideological thinking, thereby pushing Democrats to a record percentage at the top level of ideological conceptualization.

“Far more than most Democratic presidential contenders,” Wattenberg continued, “Sanders openly discussed and emphasized ideological concepts, proudly promoting progressivism and democratic socialism.” “What we saw in 2016,” the scholar explained in a recent interview, “was sort of a legitimation of talking in those terms. Bernie Sanders said, ‘Progressivism, democratic socialism, these are good things.’ For the first time, I’m really seeing that in the interviews.”

For a single candidate, in a single campaign, to leave such an imprint on mass opinion is remarkable; Obama didn’t manage that, and by all indications neither would Warren. Maybe Levitz is right when he posits that a President Warren would be better able than a President Sanders to “get senators like Jon Tester and Kyrsten Sinema to swallow marginally more progressive legislation in 2021.” Maybe. But to embrace that as our political horizon would be a counsel of despair.

The rationale for Sanders’s brand of politics has always been that shifting the basic parameters of American politics — however difficult that may be — is a better aim than accepting those parameters and trying to maneuver within them. Both the bitter disappointments and the fragile hopes of the last decade of politics have tended to prove that strategy right. Lowering our sights now would be a world-historical mistake.