LONDON - The 2020 US election is shaping up to be the biggest betting event of all time, with one player placing a record-breaking one million-pound bet on a victory for Democratic challenger Joe Biden, betting companies say.

People were still rushing to place bets on the eve of Tuesday's election and Matthew Shaddick, Head of Politics Betting at Ladbrokes Coral Group, said it estimated about one billion pounds would be wagered globally across the industry.

President Donald Trump's chances of re-election gained slightly over the weekend, but Biden remained a clear favorite in online betting markets.

Betters on British exchange Smarkets give Biden a 65% chance of winning, while Trump's prospects improved to 35% from 34%.

UK-based internet Betfair Exchange said it also saw Trump's odds improve on the same level.

One person had placed a one million-pound ($1.3 million) bet on Biden, Betfair said, the biggest political bet of all time. If Biden wins, the player would bag 1.54 million pounds.

The former vice-president has a substantial lead in national opinion polls, although the contest is slightly closer in battleground states likely to decide the race.

"Florida is one where the polls suggest Biden is the more likely winner, but the (betting) markets have Trump as favorite," Shaddick said.

"The GOP have tended to overperform the polls quite regularly in that state."

The election is on track to be by far the biggest betting event, with 271 million pounds bet so far, Betfair said. It accepts bets right up until the result is announced and sees bets with it to hit the 400 million pound mark, double that of 2016.

Most of the big-money betting occurs outside the United States as betting on politics is illegal there.

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