The calls come at least once a week these days, with growing urgency: friends of the Republican presidential candidates, aides to the candidates, and often the candidates themselves, wondering if Al Hoffman Jr. might be ready to lend a hand.

"How are you doing? What are you feeling? What are you thinking?" Hoffman, a Florida real estate developer who was a co-chairman of George W. Bush’s presidential campaigns, said in describing the calls.

But Hoffman, one of the Republican Party’s most sought-after fundraisers, remains unconvinced that he should tap into his extensive network of contacts to raise money for any of them.

"None of the candidates have instantly identified themselves as a leader for the Republican movement," Hoffman said. "The Bush family were instantly identifiable as leaders."

He is far from alone. Two and a half years after Bush left the White House, the formidable network of Republican donors he assembled has largely melted away. Fewer than 1 in 5 of Bush’s Rangers and Pioneers, the elite corps of "bundlers" who helped Bush smash fundraising records in his two runs for the White House and remain the gold standard of Republican fundraising, have contributed to any of the current Republican candidates, according to a analysis.

Their absence underscores the challenges facing the Republican Party in what could prove to be a protracted primary campaign followed by a hugely expensive general election matchup against an incumbent president.

No Republican candidate for president this year has yet shown the kind of broad appeal that rapidly drew the party’s donor establishment to Bush early in his first run, with only Mitt Romney, the former Massachusetts governor, raising enough money in the early going to assure being competitive through this year.

In an economy that has drained pocketbooks and inhibited the emergence of a younger class of wealthy donors, no Republican candidate has yet been able to seize the imagination and loyalty of a new generation of financial supporters. While the eventual nominee will have an opportunity to unite donors now dispersed among the sprawling primary field and benefit from the pools of money backing conservative causes, none of the candidates have yet assembled the kind of big-check network that could be confident of keeping up with the fundraising machine being built by President Barack Obama.

And some large donors, unsatisfied with the presidential field, are choosing to place their bets with the party’s congressional wing or with independent expenditure groups, which offer them the ease of writing a single check instead of the grinding work of wrangling contributions from dozens of friends and business associates.

"Nobody is inheriting any kind of apparatus left over from the Bushes at all," said Ray Washburne, a Dallas entrepreneur and former Bush Ranger who is backing Tim Pawlenty, the former Minnesota governor. "Everything’s going to have to be recreated. There are new players who want to play, and there are other people tired and done."

More of Bush’s former supporters could still emerge later in the race or after the party settles on a nominee, as many Rangers and Pioneers did for Sen. John McCain of Arizona, the nominee in 2008. Some may be awaiting the entry into the presidential race of Gov. Rick Perry of Texas, although some longtime Bush supporters said there was relatively little overlap between Bush’s network of financial supporters and the one built by Perry, a powerhouse fundraiser in his own right.

And no fundraising machine exists in perpetuity: Large networks of bundlers are built first and foremost on the personal loyalty of donors to specific candidates.

"I tried to retire last time, and I really put my foot down this time," said Bradford M. Freeman, a Los Angeles financier who led Bush’s California finance team and was among the top bundlers for McCain. "I was a very close personal friend with President Bush. It was a labor of love."

Some Republicans suggested the Bush fundraising machine rested on circumstances that would be hard for other candidates to replicate. As the governor of Texas, the son of a former president and brother of a Florida governor, Bush could tap into three of the party’s most robust networks of supporters. In his first campaign, Bush ran during an economic boom and after eight years of a Democratic administration loathed by his party; during his second, he was an incumbent during wartime.

"We put together a fundraising team that was pretty dang good," said James B. Francis Jr., a Texan who organized the Pioneer network during Bush’s first run but has not signed on with any of the current Republican candidates. "But it’s not monolithic. And obviously, when you have a completely different field, and George Bush is not in the race, people are going to go in different directions."

The fragmentation of Bush’s donor network also reflects, in part, a lull in the Bush dynasty. Bush left office in 2009; his brother, Jeb Bush left the Florida governor’s office in 2007. No Bush family member currently holds elective office, and the closest thing to a Bush campaign in politics today is Maverick PAC, a political action committee co-founded by George P. Bush, the former president’s nephew, to organize Republican young professionals.

"The day the 2004 campaign was over, you got a tie, and that was it," Washburne said.

Those of Bush’s former top operatives still working in politics are scattered around various research organizations, lobby shops and independent expenditure groups, some of which are proving attractive for major Republican donors eager to have an impact in the presidential race but unwilling to pick a candidate yet.

A. Jerrold Perenchio, the billionaire founder of Univision, was a Bush Pioneer in 2004 and a national finance chairman of McCain’s 2008 campaign. Perenchio has not yet donated to any of the Republican candidates, but in April a trust he controls donated $2 million to American Crossroads, a so-called Super PAC founded by Karl Rove, Bush’s former adviser.

Some Bush alumni said they believed a substantial number of former Bush donors had decided to cast their lots with Rove early in the cycle, rather than with the still-fluctuating Republican field.

"I don’t think the Rangers and Pioneers aren’t playing; I think they are playing in a new way," said Mark McKinnon, a former top strategist for Bush. "My guess is that many of them have determined their money is much better invested and spent in the Super PACs. A lot of them know and trust Karl Rove to give them a good bang for their buck. So that’s where their bucks are going."

Bush’s Rangers and Pioneers are still a prized commodity in Republican presidential politics, their allegiance avidly sought by most of the candidates and — once won — quietly advertised to other potential supporters as evidence of viability and establishment support.

Of those Bush bundlers still active in politics, Romney appears to have drawn the most big names, among them financier Lewis M. Eisenberg, H. Gary Morse, a Florida real estate developer, and Sam Fox, a former ambassador to Belgium.

Their support has helped Romney lap the Republican competition: During the three months ending June 30, he raised $18.25 million, four times more than any other candidate.

© 2011 The New York Times Company