The need to hold onto seats in this milk-producing, French-speaking province also explains why Trudeau resisted liberalizing the dairy industry in North American trade talks, and why he's been timid in criticizing a controversial law targeting religious minorities. And while Trudeau’s party maintains a lead across the province, the size of that lead is deceiving. The numbers are shifting quickly, with the separatist Bloc Québécois party, led by Yves-Francois Blanchet, leapfrogging past the Conservatives since the first French debate. And Trudeau's province-wide numbers are inflated by urban Montreal, hiding far closer races elsewhere in the province.

INTERACTIVE: See the latest polling numbers for Canada's election.

Outcomes in those wild four-party battles will decide the majority of Quebec’s 78 seats and, possibly, also the outcome of the Canadian election.

Quebec is Trudeau’s home province and where his seat is, though that local-son advantage is mitigated by the tumultuous relationship his Liberal Party and his late father had with the province, strained by old battles over the constitution and Quebec independence.

A longtime Liberal official says the province provides a valuable firewall for Trudeau, given the likelihood the party will lose seats elsewhere. Trudeau can only afford to lose eight seats and retain his parliamentary majority, and he’d be defeated entirely if he lost too many more.

Quebec is the one populous region where the Liberals might not only hold onto huge numbers, but even potentially make some gains. Elsewhere, they’re projected to lose seats in Ontario, Alberta and on the Atlantic Coast where they took literally 100 percent of seats four years ago and where a few popular incumbents have retired.

“It comes down to math,” the official said, speaking of Quebec. “And the fruit is ripe there.” He joked about the comparative stability of American elections, compared with Quebec’s: “What we call a ‘wave’, you call a ‘tsunami.’”

Quebec’s uniquely combustible campaigns stem from old feuds over Quebec independence; the rise of new parties; four-way parliamentary races; and fluid partisan self-identification. The result: Distant also-rans have a history of instantaneously catapulting from second or even third place into first, raking in scores of House of Commons seats that determine Canadian election winners.

For the sake of comparison, imagine this scenario unfolding in the U.S.: A third party, just slightly more visible than the Libertarians or Greens, mutates, within days, into an electoral colossus that gobbles up three-quarters of the districts in the U.S. House of Representatives in a 325-seat wave.

Impossible, right? Well, it’s roughly what happened in Quebec in 1984, 1993, 2011 and 2015; four different parties transformed instantly into electoral behemoths.

Ask Laurin Liu. She has personal experience with two past waves — one that carried her into Parliament, the other out of it.

She's one of four college students who went from being part of McGill University's campus club for the New Democratic Party to becoming members of Parliament in the unexpected wave of 2011. Liu was 20 and only agreed to include her name on a federal ballot because the left-leaning NDP couldn’t find candidates to run in the no-hope ridings outside Montreal. She consented, because she supported the party and wanted to help it field a full slate of candidates.

“I was writing my final exams,” Liu said, describing her original plans for the spring of 2011. “I was so far from believing [I’d win].”

She had so little expectation of winning that she wasn’t even watching the returns on election night, and spent the evening helping another campaign count ballots. She found out she was elected in a text message from a friend, one of nearly five-dozen NDPers elected from Quebec, elevating that party to Canada’s official opposition for the first time in its history.

The best-known story of that wave involved an English-speaking bartender from Ottawa. She was elected in a distant area of French-speaking Quebec, despite her having weak command of the local language and so little expectation of winning she spent part of the campaign on a birthday trip to Las Vegas. But Ruth-Ellen Brosseau wound up improving her French, winning enough fans in her new hometown that she was reelected in 2015. A new local poll suggests she might be one of the final NDPers left standing in Quebec after this election.