Senator Tim Kaine an online favorite to run with Clinton

Senator Tim Kaine of Virginia has emerged as the online betting favorite to be presumptive Democratic presidential nominee Hillary Clinton's running mate while Bernie Sanders' chances have slipped, online predictions market PredictIt said.

Kaine topped a list of potential vice president candidates with about 20 percent probability, followed by U.S. Senator Elizabeth Warren of Massachusetts with about 17 percent and U.S. Labor Secretary Tom Perez with about 14 percent.

The website, which allows users to wager small amounts of money, said Sanders' chances of joining Clinton's race for the White House were about 10 percent. Big election wins on Tuesday catapulted Clinton to victory over Sanders, a U.S. senator from Vermont, although he has vowed to go on contesting the race.

Bets on Clinton winning the Nov. 8 U.S. presidential election were going for 66 cents while bets on Donald Trump, the presumptive Republican nominees, were traded at just 33 cents.

On the Republican side, U.S. Senator Jeff Sessions of Alabama was leading the race to be Trump's running mate at 20 percent, followed by U.S. Senator Joni Ernst of Iowa at 17 percent, former House Speaker Newt Gingrich at 15 percent and New Jersey Governor Chris Christie at 9 percent.

The latest opinion poll by Reuters/Ipsos on Tuesday showed Trump trails Clinton by 10 points in the 2016 presidential campaign, showing little change from a week ago.

The online survey had 44.3 percent of likely voters saying they would vote for Clinton, compared with 34.7 percent who would support Trump. A further 20.9 percent said they would not vote for either candidate.

PredictIt is jointly run by Washington political consultancy Aristotle and Victoria University in Wellington, New Zealand. Its users are registered U.S. voters. As with opinion polls, predictions markets do not always accurately forecast outcome.

(Reporting by Angela Moon; Editing by Howard Goller)