Former Republican presidential candidate Marco Rubio reversed course Wednesday and said he will seek re-election to the Senate, telling Fox News: “I changed my mind.”

The decision, widely expected among his Florida Republican colleagues, follows repeated claims during the GOP presidential primary race that he would not run again for Senate. 

Rubio for months had spoken about his frustrations with the Senate, in explaining his original decision to run for the presidency only – and defending himself against criticism for missed votes.

 

But he told Fox News’ Chris Wallace on Wednesday while he’s “frustrated” with the Senate, it is “also a place where you can serve your constituents” and “hopefully be able to still move on some major issues.”

Further, he said the “deepest reason” he’s running is, “I think 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.”

Rubio said by serving in the Senate, he could "encourage" presumptive GOP nominee Donald Trump to "make the right choice on some issues" if he is elected presdient. 

"I don't think it's a mystery that I disagree with Donald on a number of issues," he said.

When pressed by Wallace on his support of Trump, Rubio said while there were "a lot of things" the candidate has done he's disagreed with, that did not compare with his thoughts on presumptive Democratic nominee Hillary Clinton.

"I disagree with everything that Hillary Clinton stands for," he said.

Other factors also may have been at play in Rubio's decision. The senator, who suspended his presidential campaign in March, had come under intense pressure from senior GOP figures to reconsider amid concerns about keeping the seat in Republican hands – and he publicly opened the door to doing so after the Orlando terror attack.

“It really gives you pause to think a little bit about, you know, your service to your country and where you can be most useful to your country,” Rubio told radio host Hugh Hewitt during an interview last Monday.   

Rubio faced a June 24 filing deadline to make the decision.

Others in the Florida Senate race had been girding for Rubio’s entry into the race. On Friday, Rep. David Jolly bowed out of the contest to make way for a potential Rubio run. Jolly said he will seek re-election to the House instead. 

Lt. Gov. Carlos Lopez-Cantera and U.S. Rep. Ron DeSantis also said Tuesday, in light of Rubio's decision, that they would drop out of the race. But two other candidates, real estate developer Carlos Beruff and Orlando businessman Todd Wilcox, recently said they would not be pressured into abandoning their candidacies, according to the Tampa Bay Times.

Beruff recently circulated a memo that implied Rubio was politically exploiting the Orlando tragedy.

“But we do now know that Sen. Rubio is by his own admission rethinking his decision not to run, and he is saying that his rethinking is somehow connected to the evil act of terrorism in Orlando,” wrote Beruff adviser Curt Anderson in the memo obtained by Politico.

The winner of the GOP primary will face off against either House Democrat Patrick Murphy or fellow Rep. Alan Grayson.

Florida's primary elections are Aug. 30.