A conviction in the New York criminal case against President Trump could propel President Biden into a national lead in the 2024 presidential election, according to a new survey.

The Marquette University Law School Poll finds that, nationally, among likely voters, Mr. Trump leads Mr. Biden 51 percent to 49 percent.

In a five-way race, Mr. Trump leads with 44 percent support, followed by Mr. Biden with 41 percent, attorney Robert Kennedy Jr. with 11 percent, professor Cornel West with 5 percent, and the Green Party nominee, Jill Stein, with 2 percent.

The survey also asked respondents how they would vote if Mr. Trump was convicted and how they would vote if he were found to be not guilty in his New York criminal case.

In the guilty scenario, Mr. Biden led Mr. Trump 43 percent to 39 percent, with 18 percent saying they would vote for someone else. In the not-guilty scenario, respondents preferred Mr. Trump, 44 percent to 38 percent, again with 18 percent saying they would vote for somebody else.

The majority of the respondents, 54 percent, also reported thinking that Mr. Trump did something illegal in reference to the case in New York. Another 27 percent said he did something wrong but not illegal, and 19 percent said he did nothing wrong.

The question of how the New York case might affect voters’ opinions and intentions going into November has only increased in relevance as it is looking more like the other cases against Mr. Trump will not be heard before the election.

While other surveys have found that support would decline for Mr. Trump if he’s convicted, there’s been speculation as to whether the pornstar pay-out case is being taken as seriously as the former president’s election interference case or the classified documents case.

The survey also separated voters based on their opinions of Messrs. Trump and Biden to gauge the leanings of the “double haters” — voters who have an unfavorable view of both men.

“A strength of Biden has been his ability, despite his high disapproval rate, to win votes from those who ‘somewhat disapprove’ of how he has handled his job as president,” pollster Charles Franklin wrote in a memo accompanying the poll. 

Among the “double haters,” Mr. Biden leads Mr. Trump, 57 percent to 43 percent, a slight decline from the pollster’s March survey that saw Mr. Biden winning 59 percent support. 

This group of voters who have an unfavorable view of both major candidates is expected to be a key demographic in the 2024 election. According to the Marquette poll, they account for 21 percent of respondents.

The survey was conducted between May 6 and May 15. The sample of 1,033 adults included 902 registered voters and 684 likely voters. The margin of error for the likely voter model was plus or minus 5.2 points.