Former Florida governor Jeb Bush, shown addressing the Detroit Economic Club about his “Reform Conservative Agenda” in Detroit this month, is amassing a significant war chest. (Rebecca Cook/Reuters)

Jeb Bush’s money juggernaut is far eclipsing the efforts of his would-be rivals for the 2016 GOP presidential nomination, putting his two political committees on pace to amass an unprecedented sum of tens of millions of dollars by early spring.

The former Florida governor’s overwhelming dominance in the race to line up financial backers has come at a speed that has impressed longtime Republican money players, who say wealthy party backers have rapidly migrated to Bush since 2012 nominee Mitt Romney decided against another White House run two weeks ago.

At one Manhattan fundraiser for Bush at the Park Avenue home of private-equity titan Henry Kravis this week, about 25 attendees paid a minimum of $100,000 each just to get in the door. It’s one of six events for Bush’s political action committees — including one next weekend in Palm Beach — with such a price tag.

“I think they will come up with an eye-popping figure,” said veteran GOP fundraiser Fred Malek.

Bush’s press for dollars has been so intense — averaging one fundraiser a day — that his Republican competitors do not even claim they can compete at his level and acknowledge that he is the unrivaled financial leader.

“Are they raising a lot of money? Yeah,” said Ray Washburne, a Dallas real estate developer who is heading efforts to solicit contributions for Gov. Chris Christie’s new political action committee. “We’re in the making-friends stage.”

The gravitation to Bush is being driven in part by the wide network of donors who supported his father and brother, as well as a sense among many in the establishment that his policy acumen and moderate stance on immigration makes him the strongest contender in a general election.

Despite Bush’s robust lead, party strategists and fundraisers agree that there is still plenty of room for his rivals to maneuver because of the changed nature of this year’s money primary. Super PACs that can raise unlimited donations have already been embraced by the expected candidates, allowing them to scoop up massive contributions before their campaigns officially launch. And the pool of potential givers has greatly expanded in the past several years, as the freewheeling era of big-money groups has attracted a new class of political donors.

“There’s a lot more room in this environment,” said Richard Hohlt, a Republican lobbyist in Washington who is helping raise money for Bush. “I am shocked, as a person who has done this since the Nixon campaign, how there are so many mega-donors who are willing to write significant checks. The point is, candidates can stay alive a lot longer.”

Still, there are mounting signs that Bush’s financial momentum is coming at other candidates’ expense — especially Christie’s. While the donor class seems increasingly intrigued by Gov. Scott Walker of Wisconsin, enthusiasm for Christie has dimmed, according to major GOP contributors and bundlers across the country.

“Everybody says, ‘Bush, but I like Walker,’’ or ‘Walker, but I like Bush,” said one senior party figure, who declined to be named to describe private conversations with donors. “I don’t hear anyone saying Christie.”

Supporters of the New Jersey governor have been taken aback by the number of top Romney fundraisers who have already signed up with Bush.

And Christie’s stumbling remarks about child vaccines on a recent trip to London so alarmed some of his supporters that the governor had to make a round of calls to assure them that he does support vaccination for diseases such as measles, according to a person familiar with the outreach.

“Gov. Bush will get the majority of the money here, the big money,” said Theresa Kostrzewa, a lobbyist in North Carolina who backed Romney in 2012 and is now supporting Bush. “And Gov. Walker will get a fair share. But I think the interest in Gov. Christie was fleeting.

“For people in North Carolina, it’s like going on a date with the high school football star and you’re wowed, but then it’s not deep enough to form an attachment,” she said. “Then when he’s been stumbling, what little attachment there was has fallen away.”

Christie backers contest that and say he is drawing a strong response among party financiers. His allies are expected to launch a super PAC in the coming days, giving him a vehicle to pull in the kind of huge donations that Bush is getting now.

“He will have significant and sufficient funds to be very competitive,” said Bobbie Kilberg, a top Republican fundraiser in Northern Virginia who backs Christie. “We need to focus on the fact that this is a marathon, it’s not a sprint. And as long as you are competitive, you don’t have to be number one in fundraising.”

Bush advisers argue that he is actually the one playing catch-up, noting that likely 2016 contenders such as Sens. Rand Paul of Kentucky, Ted Cruz of Texas and Marco Rubio of Florida have long had leadership PACs in place.

“Gov. Bush is the only person among his contemporaries considering a run who hasn’t had a political operation,” said spokeswoman Kristy Campbell, who said his travels across the country have been aimed at introducing him to both donors and voters alike. “A lot of this is really about reconnecting with people.”

Party fundraisers in various camps say that many prominent GOP money figures remain undecided, including a large number of wealthy donors who were hoping Romney was going to run again. Two of the biggest players, hedge fund manager Paul Singer and New York Jets owner Woody Johnson, have not yet committed to anyone, according to their spokesmen.

Some wealthy donors also say they plan to hold off pledging themselves to a single contender, eager to see how the field develops.

“We’re going to dabble in the beginning and try to help people get their message out, probably more than one,” said Frank VanderSloot, chief executive of an Idaho nutritional-supplement company, who said he is most intrigued by Walker, Rubio and Bush, “probably in that order.”

“We’re watching really carefully, and we think each of them have different assets,” he added.

The 2016 money race kicked off early with the launch of two pro-Bush political committees on Jan. 6, both named Right to Rise. One is a super PAC that can accept unlimited personal and corporate donations and another is a leadership PAC that can take donations up to $5,000 a person. Donors and fundraisers have been urged to meet presidential campaign-style goals by March 31, with tiers of $50,000, $100,000, $250,000 and $500,000, according to people involved in collecting checks.

Bush is already using his growing war chest to shower money on key GOP officials and state parties. On Friday, his leadership PAC announced it had doled out $122,800 — including $10,000 a piece to the state parties in Florida, Iowa, Nevada, New Hampshire and South Carolina.

On Tuesday, Bush is scheduled to headline two more fundraisers in the Washington area: a mid-morning event at the offices of the powerhouse lobbying shop BGR Group and a pricier reception at the McLean, Va., home of DLA Piper partner Jamie Wareham and his wife, Laura. Among the three dozen co-hosts for the latter — who each donated or raised $25,000 — are former George W. Bush White House counsel C. Boyden Gray; Bush’s younger brother Marvin with wife, Margaret; and his sister Doro and her husband, Bobby Koch.

Next week, the former Florida governor is slated to hit Chicago and Palm Beach for more finance events.

Bush’s nonstop fundraising pace stands in marked contrast to the low profile of the leading potential Democratic nominee, Hillary Rodham Clinton, whose decision to hold off announcing whether she is running has hampered the ability of a key super PAC ally to secure financial commitments.

The former Florida governor appears to be following a playbook used by his brother, then-Texas Gov. George W. Bush, who stunned the Republican presidential field in 1999 by raising a then-staggering $37 million in his first four months of active campaigning.

Jeb Bush — who has yet to even officially announce his candidacy or set up a campaign committee — is expected to be building a much larger war chest, though his aides dispute reports that they have a $100 million goal.

His committees are not required to report their receipts to the Federal Election Commission until mid-July, but Bush could voluntarily announce his fundraising haul earlier.

While the figure is expected to be daunting, party fundraisers said other candidates will be able to remain competitive with the help of independent groups fueled by just a few wealthy patrons.

“It’s just a completely different world,” said Mississippi-based political strategist Henry Barbour, noting that Newt Gingrich and Rick Santorum were both bolstered in their 2012 bids by allied super PACs.

Such groups will play “an increasingly important role” this year, said Barbour, who expects many will not only work to run down the opposition, but will focus on building up their own candidates.

“It’s driven by dollars,” he added. “For some of these candidates, it will be a whole lot easier to raise $20 million into a super PAC, while a campaign may only be able to raise $5 or $6 million.”

Since candidates cannot coordinate with independent groups once they officially announced their bids, Barbour noted, “whoever is running that super PAC is going to have to be pretty innovative.”