The dollar softened on Tuesday as traders squared positions on the day of the US presidential election, after recent polls dented some market bets on a victory for Republican Donald Trump.

Democrat Kamala Harris has also experienced improving odds on election gambling sites and had a slight lead on PredictIt overnight, although Polymarket continued to show Trump as favourite.

In recent weeks, financial markets and some betting platforms had leaned strongly in favour of a win for Trump, whose tariff and immigration policies are considered inflationary by analysts, leading to a rise in US Treasury yields and gains for the dollar.

Overnight, though, the US currency slumped as much as 0.76 percent against the euro to a three-week trough after a weekend opinion poll showed Harris with a surprise lead in Iowa, a traditional Republican stronghold. Overall, polls continue to show a tight race.

The dollar index , which measures the currency against six major peers including the euro, edged down slightly to 103.89 as of 0618 GMT, after slumping as low as 103.67 on Monday for the first time since Oct. 21. Last week it surged to the highest since the end of July at 104.63.

The euro edged up to $1.0879, after lifting to $1.09145 in the previous session for the first time since Oct. 15.

Sterling was slightly higher at $1.2959.

Against the yen, the dollar traded at 152.34 , after slipping to 151.54 overnight, a one-week low.

"We judge financial markets are now positioned for a Harris win," said Carol Kong, a currency strategist at Commonwealth Bank of Australia.

"The USD can therefore fall modestly by 1 percent‑2 percent this week if Vice President Harris wins and lift materially if (former) President Trump wins," she said. "Any delays and/or disputes over vote counting can also add to currency volatility this week."

The winner may not be known for days after Tuesday's vote, though Trump has already signalled that he will attempt to fight any defeat, as he did in 2020.

Overnight implied volatility options for euro/dollar spiked to the highest since November 2016 on Tuesday, as did those for the dollar-Mexican peso pair . Mexico stands to be among the hardest hit by any protectionist Trump policies.