Stephen A. Schwarzman, the billionaire chairman and chief executive of the Blackstone Group, said he would back former President Donald J. Trump in the 2024 election, a reversal from his call for a “new generation of leaders” after the midterm elections.

“The dramatic rise of antisemitism has led me to focus on the consequences of upcoming elections with greater urgency,” Mr. Schwarzman, who is Jewish, said in a statement on Friday.

He also said that he was backing Mr. Trump because he believed “our economic, immigration and foreign policies are taking the country in the wrong direction.”

Mr. Schwarzman, a lifelong Republican and megadonor to the party, had stuck by Mr. Trump after his defeat in 2020 and the Jan. 6, 2021 attack on the Capitol, but turned away from him after many of the candidates Mr. Trump had handpicked lost their midterm races in 2022.

Days after the party’s disappointing performance then, Mr. Schwarzman vowed to support a new candidate in the Republican presidential primaries. But ultimately he stayed out of the primaries, according to filings with the Federal Election Commission, instead donating to Republican House and Senate candidates and the political committees backing them.

On Friday, he noted that he would continue to support “Republican Senate candidates and other Republicans up and down the ticket.”

He has donated tens of millions of dollars to Republican political committees in recent election cycles, including those used by Mr. Trump in the 2020 election.