Donald Trump is 7-2 (22 percent chance) to beat his rival, with the possibility of the incumbent being re-elected for another four years “looking less and less likely,” the betting site said.
Several other UK-based bookmakers gave Biden similarly short odds of winning the presidential contest, with BetVictor, BetFred and William Hill all offering 1-5.
Pundits rely on betting markets in Europe and elsewhere as political gambling is banned in the U.S.
Biden is currently ahead in terms of both the popular and Electoral College votes, but millions of votes are yet to be counted and the final result is not expected for hours or even days.
Fluctuations in the betting markets put Trump out ahead late on Tuesday night after it emerged that the Republican Party was faring better than polls had predicted in a number of states.
But odds of a Trump victory began to lengthen during the day on Wednesday after more votes were counted and projections for states were updated.
Prominent pollster Nate Silver, who runs FiveThirtyEight, said the Democrat camp should expect its tally to increase as ballots are counted. “There are a LOT of uncounted votes in CA, NY, MD, MA, NJ and IL,” he tweeted. “Biden’s popular vote margin is going to expand quite a bit.”
Trump claimed overnight without evidence that the election results are “a major fraud” and vowed to take the process to the Supreme Court.
In a tweet on Wednesday morning, he said: “Last night I was leading, often solidly, in many key States, in almost all instances Democrat run & controlled. Then, one by one, they started to magically disappear as surprise ballot dumps were counted. VERY STRANGE, and the ‘pollsters’ got it completely & historically wrong!”
Biden’s team said they were confident of taking four states which are yet to announce their final tallies—Wisconsin, Michigan, Nevada and Pennsylvania. Doing so would push Biden over the 270 Electoral College vote line, handing him the presidency.
A record £434 million ($562 million) has now been bet on the outcome, including £219 million on Biden and £207 million on Trump.
Betfair spokesperson Sam Rosbottom said: “Joe Biden is now the clear favorite at 1-4 to win the U.S. election—the best odds he’s ever been.
“Donald Trump is currently a 7-2 shot with the president behind in a number of key states needed to secure his re-election.”
