Signs are growing that Florida Sen. Marco Rubio is moving towards a run for reelection, a reversal of his past statements committing to retire from the Senate at the end of his term and denouncing the office as ineffective.

A major fundraiser for Rubio’s presidential bid confirmed operatives have been instructed to begin laying the groundwork for a run and are working on lining up donors — but emphasized Rubio hasn’t made the final decision yet.

“I think it’s making sure things are in place should he make the decision," the fundraiser said. "It’s fair to say everything he says publicly is what he says privately, it’s ‘if I decide to do this.' "

The filing deadline for the primary is next Friday. Rubio is expected to announce his decision as early as Monday, after consulting with his family this weekend, and allies warn that he could easily decide against it. But the fundraiser said Rubio and his team have been tapping much of his fundraising and political network from his presidential bid to ready them for this race.

“We’re expecting early next week a yes or a no," the source added. "He could change his mind one way or another, but they are preparing for a yes."

Related: Why Republicans are begging Rubio to run for the Senate

The rapid shifts in the Republican primary this week also offered clues that Rubio loyalists — and the senator himself — were working behind the scenes to whittle the field for his entry.

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On Wednesday, a Rubio loyalist acknowledged that “a number of dominoes would have to fall” before he decided to run again, noting the crowded Florida GOP primary would have to thin considerably before Rubio would jump in the race.

The first to fall this week was Florida Lt. Gov. Carlos Lopez-Cantera, who told Politico in an interview on Wednesday he encouraged Rubio this weekend to “reconsider” a run for reelection.

Lopez-Cantera’s comments were described by three Rubio loyalists as the clearest indication yet that Rubio's leaning towards another run. He remains close friends with Lopez-Cantera, and was even planning to headline a fundraiser for him next week. The blessing — tied up neatly in an evocative personal tale complete with a pre-sunset heart-to-heart in a truck — would be the key Rubio would need to move forward with a bid.

On Friday, Rep. David Jolly became the latest of those dominoes to fall, exiting the Florida Senate race to run instead for reelection to his House seat. Polling’s shown him competitive against Democrat Charlie Crist. Hours before announcing his plans, Jolly said on CNN that Rubio is “saying he’s getting in” to the Senate race.

Rep. Ron DeSantis has also said he’d reconsider his Senate bid if Rubio jumps in. Many Florida political observers believe DeSantis also has his eye on an attorney-general bid in 2018, and the backlash he’d face among Florida Republicans if he continued his Senate bid could damage his long-term prospects in the party.

Two candidates have indicated they’ll run regardless of what Rubio does — businessmen Todd Wilcox and Carlos Beruff — but Wilcox has failed to get traction in the primary. Beruff remains a wildcard — he just signed on Florida Gov. Rick Scott’s former campaign manager, and has already spent more than $3 million of his own money on the race.

Related: Where does Marco Rubio go from here?

But Rubio will have the force of multiple big-money GOP groups behind him, and he’ll be able to tap much of the same network that helped catapult him from long-shot underdog to favorite of the GOP establishment in his presidential race. Rubio’s former communications director, Alex Conant, noted he’s just launched a new consulting firm with Rubio’s former campaign manager, Terry Sullivan, but said in an interview “he’s got my full support.” A number of longtime supporters privately echoed those comments.

Still, it would be a remarkable shift from Rubio’s repeated insistences that he wouldn’t run for reelection. Just one month ago, Rubio quipped on Twitter: “I have only said like 10,000 times I will be a private citizen in January.”

It’s also a risky move for the senator, who’s expected to easily win the primary, but face a much tougher fight in the general against Democratic Rep. Patrick Murphy, especially in a presidential year. A loss for Rubio could mean the end of his political career, which are dire stakes for a Republican who could make another bid for the presidency in 2020 or 2024.

Related: Something's Up Between Trump and Rubio

Rubio’s former aides privately acknowledge he’ll have a tough fight in the general, and could even take some bruises in the primary. Rubio’s presidential campaign pollster Whit Ayres noted that the GOP presidential nominee is one factor that would make both races difficult.

“Running both a primary and a general election campaign with Donald Trump at the top of the ticket is challenging,” Ayres said.

Multiple Rubio allies, including Ayres, also admitted Rubio’s criticism of the Senate during his presidential run — he said last November “I’m frustrated at my time in the Senate because nothing happens” — and the repeated insistence he wouldn’t run for reelection could come back to haunt him.

Asked how Rubio could overcome the issue, Ayres offered, “It all depends on how good of a candidate you are.”

But that’s the one thing Rubio’s aides have always believed about their candidate — that he’s one of the best communicators the party has. His reelection fight might be just another chance for him to prove it.