Updated 6:19 p.m. | Marco Rubio on Monday became the third Republican senator to announce a bid for president and the first of the group to leave behind a competitive seat.  

Rubio vacating his seat in Florida in favor of national ambition gives the GOP another potentially strong White House contender. But it presents new challenges for Senate Republicans pushing to hold their newly acquired majority by leaving an expensive open seat in a state at the heart of the presidential election.  

Two days before Rubio’s formal Monday night announcement in Miami, the race to replace him had already taken an unforeseen turn. Republicans thought they had a top recruit in Florida Chief Financial Officer Jeff Atwater, until he announced on April 11 he wouldn’t run. His decision leaves a wide-open field on the Republican side, with at least a half-dozen potential contenders.  

“The race has changed dramatically,” said Adam Goodman, a Republican media consultant in Florida. “There was an emerging consensus that Atwater was certainly, if nothing else, going to be given the first full shot to close out the field and move ahead with the nomination. So everyone had to wake up to the realization [on Saturday] that suddenly the world has changed.”  

Since Atwater’s exit, some Republicans have turned their sights to the congressional delegation, particularly Tom Rooney, a four-term Republican from central Florida.  

Rooney, who told CQ Roll Call two weeks ago the race wasn’t even on his radar, said in a Monday phone interview he now believes he can win the open seat and has a meeting scheduled at the National Republican Senatorial Committee Thursday.  

A potential campaign, he said, is “something that I’m taking very seriously, and I’m talking to a lot of people.” Rooney, the lone member from Florida so far to endorse Rubio, noted he has lingering concerns on the effect a statewide race will have on his wife and three sons, ages 13, 11 and 8.  

Republicans are also looking at former state Speaker Will Weatherford, seen as a possible Rubio replacement for some time. The senator even mentioned Weatherford as a potential successor at a breakfast with reporters in January. But Weatherford hadn’t expressed much interest when Atwater was a seemingly certain contender, and Florida Republicans wonder if he would prefer to hold off.  

Former state Senate President Don Gaetz told CQ Roll Call on Monday he is considering a bid, saying people had begun reaching out to him in the last two days. The legislator is personally wealthy and said if he ran, he would likely help self-fund his campaign. Lt. Gov. Carlos López-Cantera, a Rubio ally, is also reportedly considering a bid and could appeal to Hispanic voters in the Sunshine State.  

Rep. Ron DeSantis, who represents a safe GOP seat based in and around Daytona Beach, has openly expressed his interest, and Florida Republicans expect he could be the first to announce. DeSantis hails from the tea party faction, and a consensus candidate is unlikely to deter him.  

Reps. David Jolly, Vern Buchanan and Dennis A. Ross are also contemplating bids, according to Florida Republicans.  

A spokeswoman for Jolly declined to comment until after Rubio’s announcement. Buchanan’s office said “he hasn’t ruled anything out at this point.” Ross Chief of Staff Anthony Foti said in an email to CQ Roll Call the congressman “has not reached a decision.”  

Some of these Republicans could wait until 2018, when there will be an open gubernatorial race and three-term Democratic Sen. Bill Nelson will be up for re-election. But Florida Gov. Rick Scott has expressed interest in running for Senate then, and his immense personal resources might deter other Republicans from the contest.  

With at least two GOP candidates expected to vie for the Senate seat in 2016, some Republicans fear a contentious primary could imperil their hopes of victory. The state’s late August primary would give the eventual nominee little time to recover financially and refocus their operation on the general.  

Democratic Rep. Patrick Murphy, a prolific fundraiser from South Florida, is the front-runner for the Democratic nomination.  

“We could screw this up,” Rooney told CQ Roll Call. “There is a very clear scenario where Patrick Murphy, who is a moderate Democrat, is going to inherit a bloodied Republican nominee who is not going to be able to get their act together to beat him.”  

Democrats could have a primary on their hands, as well. While Murphy is the favorite of national Democrats, Rep. Alan Grayson, a liberal firebrand, is also considering a bid. Grayson, who recently annulled his marriage of 25 years after a public court battle, has the ability to self-fund his campaign.  

Democrats, who must net five seats to ensure a majority, were already targeting the seat. President Barack Obama carried the state by razor-thin margins in 2008 and 2012, and having Hillary Rodham Clinton at the top of the ticket looks at this point like a positive for Senate Democrats.  

Rubio’s incumbency and fundraising capabilities made him a slight favorite for re-election. But as an open seat, the race is rated a Tossup by the Rothenberg & Gonzales Political Report/Roll Call.  

Related:

Marco Rubio One-Page Fact File


Marco Rubio: the CQ Biography


Open Florida Senate Seat Moves to Pure Tossup


Democrats’ Florida Senate Hopes Could Cost House Seat


How Jeb Bush Affects the Florida Senate Race


Marco Rubio Names Potential Florida Senate Candidates


Patrick Murphy Announces Senate Bid in Florida


The 114th: CQ Roll Call’s Guide to the New Congress


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