More than one-third of voters who backed Governor Haley’s primary campaign against President Trump this year will go to the polls and vote for Vice President Harris, new polling suggests. Such a high percentage could be deadly for Trump’s campaign in critical swing states. 

The new survey from Blueprint Polling, released on Wednesday, shows that 36 percent of Mrs. Haley’s supporters will vote for Ms. Harris in November. Just 45 percent say they will back Trump, while 23 percent are undecided and 6 percent will vote for a third party candidate. 

The poll was first shared with a notoriously anti-Trump digital outlet, the Bulwark. Blueprint’s lead pollster, Evan Roth Smith, told the Bulwark that, given the nature of how slim either candidates’ victory will be across the seven contested battleground states, the vice president could walk away with the election thanks, in part, to Mrs. Haley’s own supporters.

“If Harris can indeed win a third or more of them in the general election, it will provide a boost of a couple percentage points. In such a close race where the margin of victory will be razor-thin, particularly in the swing states, it’s clearly worth pursuing these voters,” Mr. Smith says. 

Many experts viewed Mrs. Haley less as a strong challenger to Trump during the primary contest, and more as the go-to option for those disaffected Republicans and independents who, while supporting conservative values and policy prescriptions, could not vote for Trump due to his own personal qualities. 

A CBS News exit poll of the New Hampshire primary — which Trump won by 11 points over Mrs. Haley — showed that 40 percent of Mrs. Haley’s voters supported her simply because they were opposed to Trump. 

If the Blueprint polling turns out to be accurate on election day, Ms. Harris could be looking at an Electoral College victory even larger than President Biden’s 2020 margin. Based on the number of voters who turned out for Mrs. Haley this year, Ms. Harris could pick up hundreds of thousands of reluctant voters across seven swing states. 

Mr. Biden won the 2020 election by a little more than 40,000 votes across three swing states — Georgia, Wisconsin, and Arizona. Based on the 2024 Republican primary results, Ms. Harris could pick up more than enough of Mrs. Haley’s former backers in those states to carry the contests, and with it the election. 

If 36 percent of Mrs. Haley’s primary supporters turn out for Ms. Harris in November, the vice president will pick up nearly 40,000 voters in Arizona — a state Mr. Biden carried by just more than 10,000 votes four years ago. In Wisconsin, Ms. Harris may garner as much as 27,000 votes, even though the president won the state in 2020 by just more than 20,000 votes. In Georgia — which was decided by nearly 12,000 votes cast — Ms. Harris could pick up another 28,000 votes. 

The biggest boon for the vice president, though, may be in North Carolina, which she is contesting with multiple visits and tens of millions of dollars in television ads through the election. Trump won the state by fewer than 75,000 votes out of more than 5 million cast.

In this year’s Republican presidential primary, Mrs. Haley took nearly one-quarter of the vote, despite the fact that she held just one rally in the state and had zero noteworthy endorsements. She took more than 250,000 votes in that primary, which means Ms. Harris could win over as many as 90,000 Haley supporters on November 5. 

Mrs. Haley made a last-minute appearance at the Republican National Convention this summer to offer what could best be described as a tepid endorsement of the former president, saying that they disagreed on a lot, but that he would be a better president than Mr. Biden or Ms. Harris. So far, Mrs. Haley has not been invited to do a single campaign event for Trump, even as he bleeds support from women voters. 

The vice president has spent much of her campaign making the case that she is a safe bet for those Republican voters who have reservations about Trump this year. At the Democratic National Convention in August, several former Trump advisors and prominent Republican elected officials spoke on Ms. Harris’s behalf. In Wisconsin on Thursday, the vice president rallied with Congresswoman Liz Cheney, who called Trump “a threat unlike any we have faced before.”