In the final week before Election Day last November in Virginia, where the commonwealth was electing a new governor, the polls were tightening. Republican Ed Gillespie, was, like Donald Trump before him, tapping into immigration fears by running campaign ads about the threat of the violent MS-13 gang and sanctuary cities. Polls showed Gillespie was suddenly within 3 points of the Democratic front-runner, Ralph Northam, who had held a sturdier lead for much of the year. Were Democrats about to blow another big race in a battleground state? Were last minute Republican efforts to exploit racial fears actually working? Could Northam lose even with an unpopular president in the White House? That scenario would defy the logic of every previous off-year election in modern times, but never mind. The punditry machine, huffing Twitter fumes, gassed itself up. The day before the election, three out of four panelists on MSNBC’s Morning Joe solemnly predicted a Northam loss.

The fourth, Harold Ford Jr., predicted a toss-up, but not without pre-writing an obituary. “Democrats are going to look back and wonder, if he does not win, did we lose on the crime issue, did we lose on the public-safety issue?,” Ford offered. Meanwhile, Mika Brzezinski wondered whether the governor’s race in a state populated by 8.5 million people might hinge on “the Donna Brazile stuff,” a niche beltway Twitter scandal so forgettable that I had to Google it to recall what it was about, despite the fact that I cover politics for a living and grew up in central Virginia. Turns out Brazile wrote a book trashing Hillary Clinton’s campaign, which surely weighed heavily on the minds of voters in Roanoke.

Not only did Northam win the Virginia race, he won by 9 points, a polling error more substantial than anything we saw in 2016. Gillespie, it turns out, actually won more votes than any previous statewide Republican candidate; he had enthusiasm at his back. It’s just that Democrats had more—and they blew the doors off on Election Day. The whole spectacle was yet another blow to polling and to punditry, two industries sullied by Trump’s victory in 2016.

The Virginia result went mostly unexamined after the results came in, as everyone in politics quickly moved on to the latest Trump thing. But the question of why Northam outperformed the polls, and why polls continue to wield such mystical power over the political press, is worth keeping in mind as America prepares to head to the polls next Tuesday. Every piece of evidence we have about voting behavior during the Trump presidency—special elections in various corners of the country, public and internal polls, early voting data in key states—indicates that we are heading for a midterm election with explosively high turnout. University of Florida professor Michael McDonald, who studies voting patterns, estimated recently that almost 50 percent of eligible voters could cast ballots this year, a turnout level not seen in a midterm election in 50 years. Trump, in his way, is loudly trying to juice Republican turnout in red-leaning Senate races by demagoguing the threat of illegal border crossings, which happen to be at their lowest point in decades.

Enthusiasm in this election, though, is mostly fueled by Democrats. Aside from college-educated white women, much of the Democratic coalition in 2018 is comprised of voters—young people, African-Americans, and Hispanics—who don’t typically show up in midterm elections. And the main thing to remember about high-turnout elections, especially ones that bring non-traditional voters into the mix, is that strange things can happen. House seats once thought to be safe are suddenly in jeopardy, like Republican Steve King’s solidly red seat in Iowa now appears to be.