NEW YORK (Reuters) - Online trading platform PredictIt and bookermaker Paddy Power showed a massive reversal of fortune for U.S. presidential candidates Republican Donald Trump and Democrat Hillary Clinton on Tuesday night, as the New York businessman’s chances of taking the White House skyrocketed on both.

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Trump stunned many political experts, showing a slight edge on Clinton in several swing states after voting had ended in more than two-thirds of the 50 U.S. states.

Paddy Power put Trump’s chance of victory at 83.3 percent Tuesday and Clinton’s at 22.2 percent. The two had been in essentially opposite positions on Tuesday morning.

The Irish bookmaker stands to take a $4 million hit if Trump wins, said Paddy Power spokesman Féilim Mac An Iomaire, who said the dramatic reversal in odds was reminiscent of what it saw in the “Brexit” vote for Britain to leave the European Union.

“You could say it’s deja vu again,” said Mac An Iomaire. “Much like Brexit, it looked to be following the odds early on before a dramatic turnaround.”

While opinion polls went back and forth leading into Britain’s June 23 referendum on whether or not to remain in the EU, betting odds favored the “remain” campaign. Britons voted to leave by 52 percent to 48 percent.

A similar trajectory played out on the online trading platform PredictIt, which was launched in 2014 and is jointly run by Victoria University in Wellington, New Zealand, and Washington-based political consulting firm Aristotle International Inc.

Clinton led Trump in PredictIt’s market on who will win the White House throughout the campaign, but news of her Republican challenger’s surprise momentum sent her chance of winning the election plummeting roughly 75 percentage points from its level Tuesday morning to 5 percent.

Trump’s chance, meanwhile, shot up more than 40 percentage points to around 65 percent.

It was the first time in the entire campaign that Trump had led Clinton on the platform, according to a PredictIt spokeswoman.

British gambling company Ladbrokes had Trump’s chance of victory at roughly 85 percent Tuesday night, compared with 15 percent for Clinton.

Ladbrokes had earlier in the day placed Clinton’s chance of victory at 76 percent and Trump’s at 24 percent, but company spokeswoman Jessica Bridge said the development “isn’t a surprise in the slightest,” given the high volume of trades made on Trump since the market opened in 2012.

Roughly 75 percent of all bets in Ladbroke’s U.S. presidential wagering had been placed on Trump.