Trump takes Iowa, and a big first step toward a rematch with Biden.

Donald J. Trump won the Iowa caucuses on Monday, a crucial first step in his bid to reclaim the Republican nomination for the third consecutive electionas voters braved the bitter cold, looked past his mounting legal jeopardy and embraced his vision of vengeful disruption.

The victory, called by The Associated Press on Monday night only 31 minutes after the caucuses had begun, accelerated Mr. Trump’s momentum toward a historic potential rematch in November with President Biden that could play out on both the campaign trail and in the courtroom.

In a state that had rejected him in the caucuses eight years ago, Mr. Trump finished ahead of two of his main rivals, Ron DeSantis and Nikki Haley, both of whom were locked in a race for second place. It was unclear who had won second and who had won third.

The result was a setback for both Republicans, who had spent as much time and money battling each other in Iowa as the front-runner. Mr.DeSantis, the Florida governor, had previously predicted victory in Iowa, and both he and Ms. Haley, the former United Nations ambassador, have argued that a strong second-place finish would better position them as Mr. Trump’s chief rival going forward.

Mr. Trump is the first former president in the modern era who has sought to return to the White House. On Monday, he was hoping to shatter the Republican record for the largest victory ever in a contested caucus, which was just under 13 percentage points. Despite the quick declaration of Mr. Trump as the winner, it was not yet clear if he would win an outright majority of more than 50 percent, a critical psychological barrier for those in the party still hoping to stop him.

A spokesman for Mr. DeSantis, Andrew Romeo, said in a statement that the