On Wednesday, as Joe Biden’s pathway to the presidency of the United States appeared ever more likely than Donald Trump’s path to reelection, Australian bookmaker Sportsbet announced that it was paying out nearly $17 million in winnings to bettors who had wagered on Biden to win the White House.

Though Biden had yet to achieve President-elect status, the bookie said it had “supreme confidence” that the Democratic nominee would end up the winner—a sentiment widely echoed by betting operators and prediction markets tracking the presidential race. U.K. gambling company Betfair and London-based betting exchange Smarkets were both giving Biden an 86% chance of sealing the presidency as of Wednesday afternoon. Betfair was offering 1-to-6 odds on Biden, which would pay out only $11.67 on a $10 bet; by contrast, Trump’s increasingly remote 6-to-1 odds would have awarded $60 for the same bet.

Of course, Biden was also the favorite on virtually all betting and prediction markets heading into the election—so much so that one Betfair bettor felt confident enough to place a £1 million ($1.3 million) wager on the former vice president, at 8-to-15 odds (65% probability). Yet both Biden’s and Trump’s odds went on quite the ride as the election began unfolding on Tuesday evening—a topsy-turvy roller coaster that reflected, in real time, the evolving public perception of an unprecedented, historically unpredictable contest.

Courtesy of Smarkets

At the start of Election Day on Tuesday, Biden maintained his advantage on the betting markets, with his odds of winning the White House fluctuating from 60% to nearly 70% early in the day. And as the first polls began to close on the East Coast, Betfair gave Biden 1-to-2 odds (67% probability) of victory.

But things quickly turned in Trump’s direction as results began coming in—particularly from Florida, where Biden’s underwhelming performance in Miami-Dade County would help deliver the state for Trump. By 7:45 p.m. ET on Tuesday, with Florida results trending favorably in Trump’s direction, Betfair updated the President’s odds to give him an 82% chance of winning the state—and a 40% chance of securing reelection.

As Tuesday turned into Wednesday—and as Trump built up a strong lead in battleground states across the country—the markets completed an incredible about-face indicating that the President was in pole position to keep the White House. Trump’s odds of winning the election climbed as high as 1-to-4 (80%) at one point, according to Betfair, and stood at 4-to-7 (62%) early Wednesday morning in what the bookmaker called an “incredible turnaround.”

Yet things would soon pivot back in Biden’s direction. The Associated Press’s decision to call Arizona in the Democrat’s favor, as well as Biden’s comeback in the upper Midwest—where votes from metropolitan areas like Milwaukee and Detroit were counted later than those from Trump-heavy rural areas—swung sentiment back in his direction. By the time Biden overtook Trump in Wisconsin on Wednesday morning on his way to winning the state, betting odds had boomeranged back in his favor, with Biden back to being a 1-to-2 favorite (67% probability) to win the contest.

Since then, Biden’s odds have continued to steadily approve. Victory in Wisconsin was followed by a win in Michigan, and as votes continue to be counted from predominantly metropolitan, Biden-leaning areas in Pennsylvania and Georgia, his chances appear to only be growing—with Betfair and Smarkets each giving him as good as a 90% chance of becoming the 46th president of the United States.

Of course, that would still leave Trump with a 10% probability of winning reelection, according to the bookies. No matter how remote, he still has a chance.