Today Canadians will cast ballots in their first federal election since Justin Trudeau’s Liberals swept to power on a wave of clickbait-driven enthusiasm four years ago — and, whatever the final result turns out to be, there can be little doubt that the Trudeaumania of 2015 has finally subsided.

What initially began as a sleepy affair, with the Liberals and Tories trading superficial barbs and banalities, has since become wildly unpredictable — due almost entirely to a sudden surge in momentum for Jagmeet Singh and the social-democratic NDP. The precise causes of this shift, the predictable hot takes notwithstanding, are likely a mixture of recent events and more long-term developments.

In 2015, the Liberals gained millions of votes on the basis of Trudeau’s personal popularity and a platform many mistakenly believed was a blueprint for transformative change. Predictably enough, Trudeau soon frustrated these hopes with a run of broken promises and a refusal to implement many parts of the ultimately modest agenda he had once campaigned on.

A pledge to tax the wealthy turned into a net tax cut for the richest 10 percent of earners. Having opposed a major arms deal with the Kingdom of Saudi Arabia in opposition, the Liberals promptly signed the export permits and set to work making Canada the second-largest arms dealer in the Middle East. Those hoping for action on climate change, meanwhile, got platitudes about the economy and the environment working together, and the nationalization of a pipeline. Having courted indigenous voters in 2015, Trudeau’s government refused to implement the UN Declaration on the Rights of Indigenous Peoples in either law or spirit — pursuing the construction of new pipelines and responding to human rights rulings demanding compensation for indigenous children harmed by underfunding by challenging them in court.

Earlier this year, it emerged that Trudeau’s office had also leaned heavily on its own attorney-general to let SNC Lavalin — a major construction giant with longstanding ties to the Liberals based in Montreal — off the hook for bribery charges in Libya before the downfall of Muammar Gaddafi.

As the Liberals governed from the technocratic center, the Trudeau brand carried on as usual, creating an ever-widening disjuncture between the government’s meticulously crafted political artifice and reality. When it emerged several weeks ago that the same prime minister who had built a cloying international image as the standard-bearer for inclusive liberalism had done blackface more times than he could count, the symbolism could hardly be missed.

Given this context, the apparent surge in support for the social-democratic NDP — which has never formed a federal government in Canada — makes perfect sense. Campaigning on a more coherent and straightforwardly social-democratic program than his predecessor embraced in 2015, Singh has proven an effective communicator, particularly to voters disenchanted with the Liberals. Promising to expand Medicare to include dental and drug coverage, the NDP platform also includes a wealth tax paired with large investments in affordable housing and childcare. Its climate plan, though eschewing outright confrontation with the oil industry, also promises hundreds of thousands of green jobs and looks towards an ultimate goal of free public transit. Electoral reform, a key issue thanks to the crude disproportionality of Canada’s electoral system, is also a centerpiece, as is a ban on the racist police practice of “carding.”

In essence, the NDP’s pitch is a more tangible and cogent version of what many voters — particularly the young — mistakenly believed they were going to get with Trudeau in 2015. While Canada’s Liberals have long proven adept at absorbing and deflating the hopes and demands of progressive forces to their left, alienation with the Trudeau government and the collapse of Trudeau’s airbrushed personal brand have undoubtedly created progressive space for the NDP to occupy.

The extent to which the party’s momentum will translate into seats nonetheless remains unclear. In Quebec, the site of the party’s 2011 breakthrough, the picture is complicated by an apparent growth in support for the sovereigntist Bloc Quebecois. But in British Columbia, the prairies, urban Ontario, and Atlantic Canada it seems poised to make gains at the expense of both the Tories and Liberals.

Running with its most diverse slate in history, a number of activist left candidates also looks set to enter or reenter Parliament. Svend Robinson, a stalwart of the party’s left in the eighties and nineties, appears likely to win his riding of Burnaby North Seymour. In Toronto, where the NDP is hoping to regain seats it lost in 2015, candidates including Paul Taylor, Diana Yoon, and Min Sook Lee all have a decent shot at unseating Liberal incumbents. Indigenous activist Leah Gazan may yet achieve a breakthrough in the Manitoba riding of Winnipeg Centre and socialist city councilor Matthew Green hopes to win in downtown Hamilton. Barring electoral disaster, the next NDP caucus should also include veteran left-winger Niki Ashton — who stood for the leadership in 2017 as an avowed democratic socialist.

If the latest national polls are borne out on election day, neither the Tories or Liberals will have the 170 MPs necessary to form a majority government and the NDP will hold the balance of power in a minority parliament — leaving it well placed to extract major concessions from a beleaguered Liberal Party. Another possibility is that the polling has failed to capture the extent of NDP momentum, which would alter the final calculus more radically than most observers have considered.

In either case, from being written off mere weeks ago the NDP may well deliver a humbling rebuke to the country’s two traditional parties of government — and, if its momentum can be translated into seats, put a social-democratic program back at the center of Canadian electoral politics.