Governor DeSantis received some of his most favorable numbers since announcing his presidential candidacy in a new statewide poll out of Wisconsin, even as the governor struggles to make a dent in President Trump’s lead nationally.

In the GOP primary horserace in Wisconsin, which is expected to be a key swing state in 2024, Messrs. Trump and DeSantis are virtually tied, with 31 percent and 30 percent support respectively in a Marquette University poll released Wednesday.

Vice President Pence received 6 percent support and Senator Scott received 5 percent in the survey. The GOP primary poll had a margin of error of plus or minus 6.5 points, meaning the top-line results between Messrs. Trump and DeSantis are within the margin of error.

Key to the results in the Marquette University survey was the large portion of Republican voters who simply haven’t yet decided on a candidate — 21 percent.

When respondents in this group were asked to choose between Messrs. Trump and DeSantis with no “haven’t decided” option, Mr. DeSantis received 57 percent support to Mr. Trump’s 41 percent. Of the 21 percent of Republican respondents who were undecided in the top-line results, 74 percent supported Mr. DeSantis over Mr. Trump when forced to choose.

The numbers contrast with Mr. DeSantis’s relative stagnation in national polling. For nearly three months Mr. Trump has enjoyed majority or near-majority support in the GOP primary, according to FiveThirtyEight’s average of polls. Mr. DeSantis, on the other hand, has been struggling to maintain 25 percent support.

On the Democratic side, President Biden enjoys 49 percent support. Attorney Robert Kennedy Jr. received 9 percent support and activist Marianne Williamson received 3 percent support.

In the general election, Mr. Biden had a favorable matchup against the two frontrunners for the GOP nomination, though results in his matchup against Mr. DeSantis are within the four-point margin of error for the general election polling. Versus Mr. Trump, Mr. Biden leads 52 percent to 43 percent. Versus Mr. DeSantis, Mr. Biden leads 49 percent to 47 percent.

Mr. Biden’s lead, according to the survey, was driven mostly by his strong performance with independents, who preferred him over Messrs. Trump and DeSantis.

“Republicans are virtually equal in their support of either DeSantis or Trump,” pollster Charles Franklin writes. “Independents prefer Biden over DeSantis, but Biden does even better among independents when Trump is the nominee.”

In the general election, Wisconsin and its 10 electoral votes is expected to be a key state for either party. Analysts at both Washington University in Saint Louis’s Decision Desk HQ and the University of Virginia’s Sabato’s Crystal Ball have pegged Wisconsin as critical.