Ledyard King

USA TODAY

WASHINGTON – In March, Marco Rubio dismissed Donald Trump as a “con artist” and “the most vulgar person ever to aspire to the presidency.”

This past week, the Florida senator told reporters he’ll not only vote for Trump, he'd be willing to speak on his behalf at the Republican National Convention in Cleveland this summer. And he didn’t rule out the possibility of serving in a Trump administration.

Rubio said his apparent shift isn't that hard to understand. Supporting Trump as the presumptive GOP presidential nominee is an easy choice, he said, compared to the prospect of a Hillary Clinton victory at the polls in November.

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"Donald Trump will sign the repeal of Obamacare. She won’t," Rubio told reporters Thursday. "I want the successor to Antonin Scalia on the Supreme Court to be a conservative. I believe that’s the kind of judge that he’ll appoint, and I know she won’t. I want someone that will defend life. I know he will and she won’t."

Rubio said Trump earned his status as the GOP presumptive nominee at the ballot box.

"He campaigned and the voters chose him," he said. "I respect that process. And so I’m going to support him. I’m going to vote for him.”

Social media, of course, won't let him off the hook that easily.

“Rubio is truly a politician with no ideas, just a jumble of crap, ready to support any position, person, anything to help him get ahead,” progressive radio talk show host Mike Signorile tweeted.

“Stop Excusing Republicans Like Rubio For Supporting Trump Because Of A Stupid, Worthless Pledge,” tweeted the conservative blog Red State, referring to Rubio's frequent promise during the campaign to get behind the eventual nominee.

While Rubio was still a presidential contender, his rivalry with Trump featured highly charged, personal attacks.

Trump, mocked the Florida senator as “Little Marco” and poked fun at his tendency to sweat on the debate stage and drink lots of water.

Rubio said Trump was unfit for the Oval Office, citing his inflammatory rhetoric, his past support for Democratic policies and his call for deporting undocumented immigrants.

He also criticized Trump’s physical features: “You know what they say about men with small hands ... You can't trust them.”

But Rubio also consistently said he would support whomever Republican voters nominated. And on Thursday, the Associated Press announced that Trump had captured the 1,237 delegates necessary to lock up the nomination.

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Despite the heated campaign, Rubio said it’s time to move on.

“We were competitors," he said of Trump. "I don’t dislike him. I don’t have any negative feelings about him personally. I disagree with a lot of his positions. That was well established during the campaign. (But) I also think he happens to be substantially better than Hillary Clinton.”

Al Cardenas, former head of the Florida Republican Party and a Rubio confidante, said the possibility that he and many other Republicans will support Trump is a “work in progress.” But he’s not willing to judge Rubio.

“It’s a fairly quick turnaround in his conversion to becoming a supporter, but so be it,” said Cardenas, former chairman of the American Conservative Union. “I’m still not there. I guess Marco figured out a way to get there.”

Twitter: @ledgeking