Florida Sen. Marco Rubio will reverse course and run for reelection this year, he announced Wednesday.

Rubio launched an unsuccessful bid for the Republican presidential nomination this year, coming up short against now presumptive Republican nominee Donald Trump. Throughout the campaign, Rubio had repeatedly insisted he would not run for reelection.

“I know people in politics don’t like to admit they’ve changed their mind. But I’ve changed my mind,” he said in a Fox News interview on Wednesday.

Rubio, who fiercely tangled with Trump during the campaign but said he intends to support the GOP nominee, said the U.S. will need senators who will stand up to the next administration, whether it is Trump or Democrat Hillary Clinton in the White House.

“No matter who wins this presidential election, the Senate’s role of being able to act as a check and balance on bad ideas from the president I think … [is] going to matter more in 2017 than they perhaps ever have in our history,” he continued. “And that’s saying a lot given what we are facing now.”

WATCH: @marcorubio tells Chris Wallace why he changed his mind and decided to run for re-election in the Senate.https://t.co/zrqCFwcDcz — Fox News (@FoxNews) June 22, 2016





As recently as the second week of June, close Rubio advisers in Washington were convinced that talk of him running was idle chatter. Many of Rubio’s D.C.-based advisers remained unenthusiastic about the idea.

Democratic Florida operative Steve Schale, who has a friendly relationship with Rubio world and is generally favorable toward Rubio, ticked off the reasons why it was a high-risk move for the Florida Republican to run again.

“If you are running out of a sense of party loyalty, or just a fear of being out of the national conversation, then think twice,” Schale wrote on his blog. “If his goal is to be president, which I suspect has been his goal since running for the West Miami Commission in 1998, he should resist the temptation and trust what was clearly his plan up until a few weeks ago.”

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That plan had been to work with super lawyer Bob Barnett, sifting through offers for work in the private sector, and build his personal fortune — with the idea of running for president again in a few years.

But according to one source, Rubio’s wife, Jeanette Dousdebes Rubio, was in favor of him running for reelection. And other close friends and advisers in Florida, such as Adam Hasner — a lobbyist and former majority leader in the Florida House of Representatives — were also pushing him to run, this source said. Hasner has not responded to texts or phone calls.

And after the massacre at an Orlando nightclub earlier this month, Rubio began to shift. One Rubio confidant said if the senator returned to Congress, it would be to put himself “in position to shape policy” on anti-terrorism measures.

Rubio is potentially in position to be chairman of the Senate Foreign Relations Committee or the Senate Intelligence Committee in two to four years, the Capitol Hill insider said.

But even this argument stretches credulity as Rubio would potentially be running for president again by the time he assumed any such chairmanship.