Speaker Paul D. Ryan endorsed Donald J. Trump for president on Thursday, finally giving his backing after weeks of reluctance to the man who ran against the party’s establishment, of which Mr. Ryan is the titular leader.

In a column on GazetteXtra.com, Mr. Ryan made clear he believed that Mr. Trump was the best candidate to help establish the agenda that he himself wants to get through Congress. A spokesman for Mr. Ryan, Brendan Buck, wrote on Twitter that the column constituted an endorsement.

He has spoken to Mr. Trump numerous times, Mr. Ryan wrote in the column, and they met in a widely publicized sit-down in Washington a few weeks ago.

“Through these conversations, I feel confident he would help us turn the ideas in this agenda into laws to help improve people’s lives,” Mr. Ryan wrote. “That’s why I’ll be voting for him this fall.”

“It’s no secret that he and I have our differences,” he continued. “I won’t pretend otherwise. And when I feel the need to, I’ll continue to speak my mind. But the reality is, on the issues that make up our agenda, we have more common ground than disagreement.”

Word of the endorsement came just as Mr. Trump’s likely rival in November, Hillary Clinton, was delivering attack on his foreign policy positions, warning against giving the country’s nuclear codes to the Manhattan businessman.

Mr. Trump welcomed the endorsement. “I’m very pleased,” he said in an interview. “I have a good relationship with him actually. He was taken a little bit by storm because my situation was supposed to go the convention.”

Mr. Trump’s advisers hope the backing of Mr. Ryan will help pry open doors, especially those of donors who like Mr. Ryan.

Mr. Ryan had at times criticized Mr. Trump during the nominating contest, calling him out for divisive language. Like much of the party’s establishment, Mr. Ryan was said to be surprised when Mr. Trump became the presumptive nominee on May 3, hours after winning the Indiana primary and forcing Senator Ted Cruz of Texas from the race.

Three days later, Mr. Ryan told CNN that he was not prepared to support Mr. Trump until he heard more from him.

“I’m just not ready to do that at this point. I’m not there right now,” Mr. Ryan said at the time, saying the burden of unity falls on Mr. Trump.

“Saying we’re unified doesn’t in and of itself unify us, but actually taking the principles that we all believe in, showing that there’s a dedication to those, and running a principled campaign that Republicans can be proud about and that can actually appeal to a majority of Americans, that, to me, is what it takes to unify this party,” Mr. Ryan said in that interview.

But Mr. Ryan also faced pressure from members of the House Republican leadership, some of whom come from districts where Mr. Trump performed well in the primaries. (Source: The New York Times)

Story Date: June 3, 2016