Vice President JD Vance and Secretary of State Marco Rubio have both lost ground in leading the 2028 Republican presidential nomination prediction markets, according to a Newsweek analysis of Polymarket and Kalshi data.
Almost $714 million in cumulative trading volume has been recorded on Polymarket’s Republican presidential nominee market, where Vance’s odds have fallen from roughly 53 percent on September 3 to 43.8 percent on Tuesday. Rubio has fallen from 27.8 percent on August 3 to 15.1 percent.
U.S.-regulated prediction market Kalshi tells a similar, yet less dramatic, story, with Vance’s odds falling from 45.8 percent on September 3 to 43 percent, and Rubio’s from 29.5 percent on August 3 to just 18 percent, with almost $70,000 traded.
It comes after Vance acknowledged over the weekend that there was “of course” a chance he would not seek the presidency, citing his four young children and his wife’s dislike of politics.
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The prediction market movement raises an early question about whether Republicans are growing less certain about the party’s post-President Donald Trump succession plan.
But Koleman Strumpf, a professor of economics at Wake Forest University who studies prediction markets, cautioned against overstating the shift.
He told Newsweek in emailed comments Tuesday that Vance had fallen by roughly 4 points over the past week, only some of which followed his remarks.
Newsweek emailed Vance via the White House and Rubio via the State Department for comment on Tuesday.
“I think the main message is that people are not reading much into the announcement,” Strumpf said, adding that some of the movement had benefited candidates with longer odds.
Normally, when Vance's odds decline, the chances for Rubio, his presumed rival, increase.
But this time, Rubio is also losing ground, while possible alternatives such as Florida Governor Ron DeSantis and commentator Tucker Carlson remain in the low single digits.
Strumpf said the lack of a pronounced beneficiary from the latest movement may indicate that traders do not regard Vance’s comments as particularly consequential, rather than a decisive turn against the two leading names.
How Midterms Could Reshape 2028 Republican Race
“Any Republican looking at their prospects for 2028 right now may be cautious, especially anyone so closely linked to Trump and his administration,” Costas Panagopoulos, a distinguished professor of political science at Northeastern University, told Newsweek by phone on Tuesday.
Republican losses in the November 3 midterm elections could make the administration a liability for prospective successors, Panagopoulos suggested.
“My guess is that the president will be blamed, and by extension, so will anyone so closely linked to his administration and its policies, including the vice president and other high-profile members of his Cabinet,” he said. “There are still two years of the Trump administration left, and who knows what will happen.”
Thad Kousser, a professor of political science at the University of California, San Diego, said both men had been elevated by the same source of strength: their association with Trump.
“For the past decade, that has been the most powerful force in GOP primaries,” Kousser, whose research covers American politics, legislative elections and public opinion, told Newsweek in emailed comments.
“The question is whether midterm results in 2026 change that equation headed toward the 2028 cycle.”
He said control of the Senate would be a key measure of the Republican performance. If the elections prove disastrous for the party and the president, he added, proximity to Trump could turn “from an asset into a liability” for both Vance and Rubio.
Panagopoulos said this year's midterms could push the Republican Party in either direction.
One possibility, he said, is that Trump and Republicans “continue to crash and burn” amid declining electoral support, particularly if Democrats capture one or both chambers of Congress.
But Democratic victories could also give the administration a political opponent to blame for future setbacks.
“Right now, Republicans are the only game in town,” Panagopoulos said, making it difficult for the party to shift responsibility for what voters regard as its shortcomings.
That calculation could change under divided government, he said, meaning the outlook for administration figures considering 2028 campaigns will depend heavily on what happens in November.
“Republicans will need to do some soul searching after the 2026 midterms about what the party looks like post-Trump and who is best positioned to reflect those shifts,” he said.
Vance and Rubio could face greater scrutiny if the midterms cause Republicans to question the administration’s electoral appeal.
“A bad midterm result could turn proximity to power from an asset into a liability,” political scientist Daniel Schatz, who served as a visiting scholar at Harvard University, told Newsweek, arguing that the contest could “open up considerably.”
Both Favorites’ Odds Slide
The simultaneous decline in both favorites’ odds defies the usual logic of a two-person race, where one contender typically benefits from doubts about the other.
Instead, confidence appears to be dispersing across a fragmented list of possibilities.
Schatz said the missing beneficiary could reflect modest gains for several names, rather than a decisive turn toward one new favorite.
“Traders can lose confidence in the two favorites before agreeing on an alternative,” he said.
Political communications strategist Mike Fahey, founder and CEO of Fahey Communications, said the movement suggested uncertainty about the broader succession plan among those buying and selling the contracts.
“Vance and Rubio are two different political personalities, but they’re still tied to the same administration,” Fahey told Newsweek. “If confidence in that administration deteriorates, both men can suffer simultaneously.”
That does not establish that Republican voters have turned against either man. It may instead show that traders are assigning more weight to outcomes beyond a straightforward contest between them.
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Which Midterm Results Would Matter?
In addition to who wins control of Congress, geography and margins of the midterm results could reveal more about the Republican coalition.
Panagopoulos said Democratic victories in deeply Republican states such as Texas, Kansas, Iowa or Nebraska would represent a rejection that should concern the GOP.
Even narrow Republican victories in territory that the party normally carries comfortably could indicate deeper weakness, he added.
Afterward, Republicans would need to decide whether their future lies in replicating Trump’s politics or moving toward a different identity.
“If there’s a wholesale rejection of Trump and his agenda that may materialize after 2026,” Panagopoulos said, “the constellation of Republican voices might look very different.”
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Market Prices Are Not Polls
The movement does not establish that Republican voters have abandoned either prospective candidate.
“These are not polls,” Keith Gaddie, the Hoffman chair of the American Ideal at Texas Christian University, told Newsweek. “It is dangerous to view them as a proxy for public opinion.”
Gaddie said traders may be hedging while voters and party activists remain focused on more immediate contests. He added that Vance’s remarks could combine expectations management with a desire to preserve his political options.
Strumpf, however, said such concerns were less applicable to high-profile contracts that attract sustained trading. He pointed to the more than $700 million traded on Polymarket’s Republican nomination market and said transactions were taking place every second.
“While no forecast is perfect, if I could only have access to one forecast, it would definitely be the one from prediction markets,” he said. “There are trades every second. These values will go up by several times before they expire.”
That disagreement highlights the distinction at the heart of the story: Prediction-market prices may offer a rapidly updated forecast, but they do not constitute a representative measurement of Republican voters’ preferences.
Prediction-market prices can also respond to doubts about whether a candidate will enter, rather than judgments about how that person would perform in, a primary. That distinction leaves the central question unresolved. The market shows growing uncertainty around the two leading names, but evidence of a broader Republican shift would require movement among voters, donors, endorsements and prospective candidates.
Newsweek’s reporters and editors used Martyn, our AI assistant, to produce this story. Learn more about Martyn here.
Contact Newsweek editors on this story: Sam Stevenson and Dave Siminoff.