Wilfredo Lee/Associated Press

CHICAGO — Former Gov. Jeb Bush of Florida said Wednesday that he was endorsing Mitt Romney‘s bid for the Republican presidential nomination, and urged his party to bring the divisive primary to a close and coalesce behind Mr. Romney’s candidacy.

A day after a sweeping victory here in the Illinois primary, where Mr. Romney overwhelmed Rick Santorum in the popular vote and delegates, Mr. Bush is the latest influential Republican leader to urge the party to rally behind Mr. Romney. Several other leading voices in the party are expected to follow suit in the coming days, aides to Mr. Romney said, in an effort to build a movement to gently urge the three remaining candidates to not block Mr. Romney’s path to the nomination.

“Now is the time for Republicans to unite behind Governor Romney and take our message of fiscal conservatism and job creation to all voters this fall,” Mr. Bush said in a statement announcing his endorsement.

“We face huge challenges,” Mr. Bush added, “and we need a leader who understands the economy, recognizes more government regulation is not the answer, believes in entrepreneurial capitalism and works to ensure that all Americans have the opportunity to succeed.”

Mr. Romney flew to Washington on Wednesday for a fund-raising events, where he was also poised to urge members of Congress and influential lobbyists to support his candidacy and begin publicly calling for an end to the primary fight.

Mr. Bush declined to endorse Mr. Romney during the Florida primary almost two months ago because he believed Mr. Romney had not demonstrated he was the strongest nominee. An associate of his said Wednesday that Mr. Bush remains troubled by Mr. Romney’s rhetoric on immigration, but believes he is the strongest candidate and the primary has run its course.

The endorsement also served to squelch any lingering chatter that Mr. Bush could still jump into the race if Mr. Romney faltered. He had long told friends that he had no plans to do so.

Mr. Romney, who spoke to Mr. Bush by telephone on Wednesday morning, said he was grateful for the support and hoped it would help unify Republicans around his candidacy.

“He has long demonstrated an outstanding ability to bring people together,” Mr. Romney said in a statement. He added, “This is a key moment in the presidential contest and Jeb’s counsel and support will be critical in the coming months in my effort to defeat Barack Obama and turn around our country.”