DES MOINES, Iowa — Mitt Romney’s exit from the presidential campaign has unleashed a frenzy of fresh fundraising and set off a new race for the backing of donors who had remained loyal to the 2012 Republican nominee.

Big dollars were said to flow immediately on Friday to former Florida Gov. Jeb Bush, who already had won over several of Romney’s past donors. New Jersey Gov. Chris Christie claimed the support of others who were waiting on Romney to make a decision about whether to seek the White House a third time.

Tony Carbonetti, a Christie supporter and top aide to former New York Mayor Rudy Giuliani, a 2008 GOP candidate, said every major Republican donor got at least two calls on Friday — one from Christie’s people and one from those promoting Bush.

Romney, Carbonetti said, “released the hounds.”

None of the Republicans considering a run for president has formally entered the race. But most have established political committees that effectively serve as campaigns-in-waiting of varying sophistication. That step allows the politicians to raise money to pay for travel, staff and the logistics of getting ready to run for the White House.

The competition for donors to those organizations is fierce, with commitments signaling the potential strength of a nascent campaign and laying the groundwork for more fundraising to come.

Romney raised more than $57 million before the first voting in 2012, and that figure is often cited as this campaign’s benchmark.

Even before Romney’s announcement Friday, Bush had picked off several of Romney’s past supporters. Among them was Lisa Wagner, a top Midwest fundraiser for Romney in 2012 who pushed hard to win over others Friday.

“I’ve raised a million dollars in the four hours since he announced that I otherwise would not have raised,” she said. Her converts included Bill Kunkler, part of Chicago’s wealthy Crown family, who had been holding out for Romney.

“I’ll work for Jeb. Period. And no one else,” he said.

Christie had his own pickups. None was more significant than Bobbie Kilberg, a Virginia-based fundraiser who said she and her husband were all-in for the former federal prosecutor.

“We will support him financially and we will be bundlers for him,” she told The Associated Press, referring to the practice of rounding-up donations from friends, family and colleagues for a campaign.

Ray Washburne, the outgoing finance chairman of the Republican National Committee, has taken up the same position with Christie’s political action committee. Washburne said his phone started ringing early Friday.

“It’s been very, very positive. A lot of people that were kind of fence-sitters have come off the fence,” he said. “We’ve been very, very encouraged.”

Others were too upset or stunned by Romney’s announcement to decide what to do next. That includes Bill Simmons, a Washington-based donor who raised money for both of Romney’s previous campaigns.

“I haven’t fully thought about the next step,” he said.

He said Romney’s announcement was like seeing his favorite team lose in the playoffs and then having to decide for whom to cheer in the Super Bowl. “I guess I’ll watch the game a little bit.”

Romney’s flirtation with the race may have created space for a third candidate to compete alongside Bush and Christie for the support of establishment-minded donors and fundraisers.

With his exit, there is now room for someone else to step into that spot. In the hours after Romney’s announcement, several GOP donors said Wisconsin Gov. Scott Walker appeared to have the edge.

The news came at the end of a big week for Walker. He earned a standing ovation from a conservative crowd at a forum in Iowa last Saturday. The next day, he spoke to wealthy conservatives in California at an event organized by the billionaire brothers Charles and David Koch.

Walker ended the week in Washington as the guest of wealthy Republican donor Fred Malek.

“Walker fits into that mainstream group, and this means he’s getting a lot of interest and attention lately,” said Republican consultant Charlie Black.

So, too, might Florida Sen. Marco Rubio, who spent the week courting donors on the West Coast, Texas and Chicago after attending the Koch brothers’ event.

Few donors interviewed after Romney’s announcement mentioned the several candidates likely to compete to the right of Christie and Bush. That group includes Kentucky Sen. Rand Paul, Texas Sen. Ted Cruz, former Texas Gov. Rick Perry and former Arkansas Gov. Mike Huckabee.

“Mitt was going to probably occupy a different place on the shelf than me,” Huckabee said. “I don’t know that it has any impact on support, donors. It probably has a bigger impact on Jeb Bush and Chris Christie.”

South Carolina political strategist Warren Tomkins warned against singling out any one candidate, or type of candidate, as the clear beneficiary of Romney’s decision.

“It still goes back to having a good message and a good messenger,” said Tompkins, Romney’s South Carolina campaign chairman in 2012. “If you’ve got that, then at some point you get momentum, and then the money will come.”

Colvin reported from Newark, New Jersey. Associated Press writer Bill Barrow in Atlanta contributed to this report.

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