A Republican source described Lopez-Cantera as a “legitimate best friend” of Rubio’s, “not simply a political ally.”

Rubio has stopped short of officially endorsing the lieutenant governor. But this month, the senator appeared at a fundraiser in Washington for Lopez-Cantera, and Friday headlined a finance conference call for him, the GOP source confirmed.

Here’s what Rubio said when Tapper asked him if he would reconsider his plan to call it quits: “Maybe … Sure, I mean maybe. I enjoy my work in the Senate. I always did.”

But, Rubio added: “Look, I have a real good friend I’ve known for a long time who I was running for the Senate with. I didn’t run. I said I wasn’t going to, [and] he got in the race. I think he’s put in time and energy to it, and he deserves the chance to see where he can take it.”

Rubio’s comments come about a month before Florida’s June 24 filing deadline to get on the 2016 ballot.

When Rubio launched his presidential bid in March of last year, he foreclosed running for re-election to the Senate, even though the calendar allowed him to keep the option open.

Rubio said at the time that Florida Republicans, and the national party, deserved a candidate who was focused on the Senate and who could invest the time and resources it takes to prepare for what is sure to be a competitive and expensive campaign.

Florida is a swing state in presidential contests, and both sides are competing hard to win Rubio’s Senate seat. Rubio dropped out of the White House race in mid March after losing the Florida presidential primary badly to eventual nominee Donald Trump.

Rubio has since re-engaged in Senate business, filling his schedule dealing with local and national issues, which he had let lag beginning in early 2015 as he ramped up his presidential campaign. And now, Senate Majority Leader Mitch McConnell, R-Ky., is trying to prevail on Rubio to reconsider.

During a closed-door lunch Thursday for Republican senators, McConnell asked all of them to push Rubio to run. Even Trump, his old nemesis, set out a tweet urging Rubio to jump into the Senate race.

“There are just a ton of us who are really trying to get him to reconsider,” said Josh Holmes, McConnell’s political advisor and former chief of staff. “We really have grave concerns about our current prospects in Florida, and he solves every one of those concerns if he decides to run.”

One Florida Republican insider in Rubio’s orbit estimated in an interview with the Washington Examiner that there’s a 15 percent chance that the senator does in fact change his mind, where last week this operative would have predicted there was no chance of this happening.

In addition to stoking the fire with his interview on CNN, Rubio recently tweeted out that he’s never disliked serving in the Senate, a view that was accepted as common knowledge and seen as among the reasons he decided to run for president even though he is young and was in the middle of his first Senate term.

But sources say Rubio is still likely to stick by his earlier plans to leave the Capitol. Among the tells, besides Lopez-Cantera running, was Rubio’s decision to hire prominent D.C. attorney Bob Barnett to manage his transition to the private sector.

A spokeswoman for Lopez-Cantera issued a vague statement when asked if the lieutenant governor would exit the race to make way for Rubio.

“Sen. Rubio has been very complimentary of the lieutenant governor,” Courtney Alexander said. “I’ll let those comments speak for themselves.”