LONDON (AFP) - Irish bookmaker Paddy Power said Tuesday (Oct 18) it had paid out early to customers who backed Hillary Clinton to win the US election, saying it's a "done deal".

With less that three weeks to the vote, the firm paid out £800,000 (S$1.4 million) to those who put their money behind the Democrat, after the odds of a win for Republican rival Donald Trump plunged.

The bookies said they had seen a flood of money on Clinton over the past week following Trump's lewd comments about women and accusations against him of sexual assault.

"Trump gave it a hell of a shot going from a rank outsider to the Republican candidate but the recent flood of revelations have halted his momentum and his chances now look as patchy as his tan," said a spokesman for Paddy Power.

"Recent betting trends have shown one-way traffic for Hillary and punters seemed to have called it 100 per cent correct... it looks as though America are going to put a woman in the White House."

Before the payout, the bookmaker put the chances of a Trump win at 9/2 - a far cry from his initial 100/1 odds last year, but comfortably below the 13/8 odds of May 2016.

The bookmaker has called it right in the past, paying out US$700,000 on Barack Obama winning in the 2012 elections, two days before the vote.

But if Trump overturns the odds and becomes president it will trigger the biggest political payout in bookmaking history, Paddy Power said.