Mr. Bush’s fall to No. 2 in the markets represents a sharp shift from earlier this month, when Mike Murphy, the head of Mr. Bush’s Right to Rise super PAC, boasted to Bloomberg Politics that “if you look at the prediction markets overseas, which are kind of interesting, because that’s the one place real money’s involved, we constantly rank number one,” adding, “The smart money’s figured this out.”

As Mr. Bush’s star has faded, that of Mr. Rubio has brightened. Mr. Rubio, who is set to appear Sunday morning on CNN’s “State of the Union” political talk show, shares many similarities with Mr. Bush. Both are Florida-based mainstream conservatives who are popular among Hispanics. In some sense, this shift from Mr. Bush to Mr. Rubio is just a rebalancing as to which establishment candidate is expected to win the nomination.

There is no single prediction market that informs this assessment, but rather an array of markets in which traders either trade stock tied to candidates’ fortunes, or bet on their preferred candidate to win. (Both parties are traded, and Hillary Rodham Clinton’s chances are now at 89 percent among the Democratic field.)

Traders at Betfair, which is the world’s largest betting exchange, but which doesn’t take bets from Americans, rate Mr. Bush a 20 percent chance to win the nomination, while Mr. Rubio is given a 29 percent chance. Over at PredictIt, which is a small-scale experimental prediction market popular among American hobbyists, traders have moved more decisively, giving Mr. Bush a 24 percent chance, compared with Mr. Rubio’s 40 percent. (A peculiar inefficiency in that market tends to overrate the chances of all of the candidates, so both of these numbers are surely too high.)