Donald J. Trump won Indiana’s Republican primary on Tuesday, moving him closer to claiming the party’s presidential nomination and delivering a devastating blow to Senator Ted Cruz and other Republicans hoping to stop him.
Mr. Cruz had pinned his hopes on Indiana, which seemed to offer one of his best chances to deny Mr. Trump the delegates needed to secure the nomination before the party convention in July.
But Mr. Trump, after obliterating his rivals in five states in the Northeast last week, held a strong polling lead in the state, which had 57 delegates up for grabs.
Mr. Trump’s victory puts him in a commanding position to clinch the nomination on June 7, when the last Republican contests are held.
Mr. Trump’s victory was an extraordinary moment in American political history: He is now on course to be the first standard-bearer of a party who has not served in elected office since Dwight D. Eisenhower, a five-star general and the commander of Allied Forces in Europe during World War II.
Mr. Trump, a real estate tycoon turned reality television celebrity, was not a registered Republican until April 2012. He has given hundreds of thousands of dollars to Democrats, including his likely general election opponent, Hillary Clinton. And, at various points in his life, he has held positions antithetical to Republican orthodoxy on almost every major issue in the conservative canon, including abortion, taxes and gun control.
But none of this stopped him from driving nearly every other Republican from the race for the nomination. With his ability to speak to the anxieties of voters, and his shrewd use of celebrity and memorable put-downs, he systematically undercut veteran politicians in a field of candidates that many in the party had hailed as the strongest in at least three decades. And he did so while spending far less money than most of his rivals and employing only a skeletal campaign staff.
“It is extremely extraordinary that Trump will be the nominee for the G.O.P. this year — who saw this coming?” said Dewey M. Clayton, a professor of political science at the University of Louisville. “He has tapped into the mood of many disaffected voters who like his business success and straight talk. He is unapologetic, and many voters like this.”