While the belief that the 2020 election was stolen appears to have fueled President Trump’s win at the Iowa caucuses, the reluctance of voters who acknowledge the legitimacy of the 2020 election results to support Mr. Trump could hurt the former president in future elections.

Mr. Trump swept through the Iowa caucuses Monday night with 51 percent of the vote, compared to Governor DeSantis’s 21.2 percent and Ambassador Nikki Haley’s 19.1 percent.

There was, though, one group of Republican caucus goers that stood out for their lack of support for Mr. Trump — Republicans who said that they think President Biden was the legitimate winner of the 2020 presidential election, according to entrance polling conducted by multiple news networks.

Among Republicans who acknowledged Mr. Biden’s victory, only 11 percent supported Mr. Trump. A majority, 53 percent, supported Ms. Haley. Another 29 percent supported Mr. DeSantis, and 6 percent supported businessman Vivek Ramaswamy.

Alongside Republican caucus goers who said they would not support Mr. Trump should he be convicted of a crime, this was the cohort of Republicans least likely to support him.

The problem for Mr. Trump, though, is that while 66 percent of those polled said they don’t think the 2020 election results were legitimate, 29 percent said that they did. Among the general public, the proportion who acknowledge the 2020 election results is much larger.

A national survey from Monmouth University, released in June, asked voters, “Do you believe Joe Biden won the 2020 election fair and square, or do you believe that he only won it due to voter fraud?”

Among registered voters who responded to the survey, 60 percent said that Mr. Biden won fairly, while 31 percent said he won because of voter fraud. The data for all voters stand in contrast to the prevailing belief among Republican voters, just 21 percent of whom said Mr. Biden won fairly; 68 percent said he won because of voter fraud.

Among Democrats, 93 percent said that Mr. Biden won fairly compared to 3 percent who said he did not. Among independents, 58 percent said Mr. Biden won fairly, and 27 percent said he did not.

The managing editor at Sabato’s Crystal Ball at the University of Virginia Center for Politics, Kyle Kondik, tells the Sun that Mr. Trump’s struggles with voters who believe the 2020 election results are legitimate are related to his struggles with moderate voters more broadly.

“Trump is much stronger with very conservative and evangelical voters in this primary season compared to 2016,” Mr. Kondik says. “However, he’s also weaker with moderate voters, and those are the kinds of voters that, in a general election contest, are more up for grabs.”

Looking at the Iowa caucus entrance polls, Mr. Trump only won a majority of caucus goers, 61 percent, who considered themselves “very conservative,” a group that made up 52 percent of respondents.

Among caucus goers who consider themselves “somewhat conservative,” a group that accounts for 37 percent of respondents, 47 percent support Mr. Trump. Among those who considered themselves moderate or liberal, 11 percent of caucus goers, 22 percent supported Mr. Trump.

Mr. Kondik noted that despite apparently soft support among moderate voters, “Trump’s general election polling has been decent against Joe Biden,” adding that “of course the election is still far away.”