By Jeremy W. Peters, March 15, 2016

MIAMI — Senator Marco Rubio of Florida, who ran for president offering his youthful optimism and Cuban-American heritage as the embodiment of a new and more diverse generation of Republican leadership, but ultimately failed to galvanize voters in a much darker mood, said on Tuesday that he was suspending his presidential campaign.

Mr. Rubio made the announcement during a speech at his campaign headquarters in Miami after losing his home state by a large margin to Donald J. Trump.

Mr. Rubio hushed the boos from the audience when he congratulated Mr. Trump.

“No, no, no,” he said, interrupting the jeers. “Guys, we live in a republic and our voters make this decision. We respect this.”

Mr. Rubio, 44, was felled by many of the same forces that drove other contenders from the race: a deep anger at the Republican leadership, a level of mistrust among the party’s most motivated voters, a field of candidates splitting up the vote, and an inability to stop Mr. Trump from exploiting all those factors.

But Mr. Rubio also notably lacked what both Mr. Trump and Senator Ted Cruz could boast of: victories in a string of early nominating contests. Mr. Rubio carried only Minnesota, along with Puerto Rico and the District of Columbia, sapping his campaign of critical energy and fueling the perception — no matter how hard he tried — that he was incapable of winning the nomination.

He claimed to be the only candidate who could unite the Republican Party, but he could never unite enough voters behind him to persuasively make that case.

And one crucial shortcoming was out of his control: his youth. Many Republicans were simply unwilling to entrust the presidency to a young first-term senator.[More]