President Bush and his political advisers appear to have no clear favorite among the men - there are no women, at least not yet - preparing to run. For their part, the prospective candidates are looking for ways to contrast themselves with Bush instead of trying to imitate him.
Strategists say it would be a mistake to campaign as an extension of Bush, even though he is the first two-term Republican in the White House since President Ronald Reagan.
"You can't be the third term of Bush," said Ron Kaufman, a longtime party official and adviser to Bush's father. "People want change. They want a different direction."
Unlike most presidents, Bush has no apparent political heir. Usually, a vice president would fill that role. But Dick Cheney, with a history of health problems, has said that he won't be a candidate. The president's brother Jeb, barred from seeking re-election as Florida governor, has said he isn't interested in 2008.
That has left the potential candidates chasing what many have called the most wide open Republican nomination in more than half a century. The campaign will get a very early, and very unofficial, start this weekend in Memphis, where hundreds of activists from 26 states will hear the first drafts of stump speeches by most of their party's '08 candidates.
Sen. John McCain of Arizona, regarded by many as the man to beat, will headline tonight's session. Other presidential possibilities at the Tennessee event include Govs. Mitt Romney of Massachusetts and Mike Huckabee of Arkansas and Sens. George Allen of Virginia, Sam Brownback of Kansas and Bill Frist of Tennessee. Potential candidates who won't be there include Gov. George E. Pataki of New York, Sen. Chuck Hagel of Nebraska and former New York Mayor Rudolph W. Giuliani.
Bush remains popular among Republican voters, particularly those who participate in presidential primaries. As a result, no Republican is expected to mount an aggressively anti-Bush campaign like Patrick J. Buchanan's 1992 challenge to Bush's father. Still, the president's second-term fade in the polls has potential successors easing away.
"There is a sense on the Republican side, and you've really seen it in the last two months as the [Bush poll] numbers haven't gotten any better, that '08 can't get here fast enough," said Tom Rath, a New Hampshire Republican who is close to the White House. "There is a sense of moving on, quicker than I've ever seen it. And it may just be because there's no obvious successor and people are doing things more quickly."
As they gear up to run, Republican hopefuls are putting distance between themselves and Bush on matters of substance.
"Of course I'm going to say that my president is a great president," said Romney, one of the most active of the early contenders. But Romney practically leapt at the opportunity to spell out his differences with Bush during a recent interview on Fox News Sunday. Among them: the president's failure to place more troops on the ground after the initial invasion of Iraq and Bush's decision to add a costly drug benefit to Medicare without reforms to pay for it.
The Bush administration's approval of the Dubai port deal has brought criticism from throughout the party. Pataki was seriously ill and being fed intravenously when the furor erupted. But that didn't stop the hospitalized hopeful, who has already made multiple visits to the key states of Iowa and New Hampshire, from issuing a statement opposing the deal and threatening legal action.
Other Republican presidential possibilities quick to criticize the port transaction, or Bush's handling of it, included Frist, the Senate majority leader, who earlier split with the president over federal funding of stem cell research. Huckabee said he was troubled by Bush's "confrontational manner" in defending the port deal, which "created almost an impossible situation for governors and members of Congress."
A notable Bush defender in the port fight is McCain, whose well-earned reputation as a maverick insulates him from claims that he's too close to the president. McCain was Bush's toughest opponent in the 2000 Republican campaign and, in a recent showdown, forced the president to reverse himself and agree to a ban on torture of detainees by U.S. personnel.
Virginia's Allen, whose cowboy boots and sunny brand of conservatism make him the nearest thing to an '08 Bush clone (detractors call him "Bush lite"), isn't hesitating to buck the president. He helped sink the nomination of Harriet E. Miers to the Supreme Court by pointedly refusing to endorse her and saying that he wished Bush had nominated someone else.
The eagerness with which GOP contenders are carving out space between themselves and the president is matched on the other side by an apparent Bush effort to keep the president's most prominent supporters and advisers away from the '08 race for as long as possible.
Some insiders say the White House quietly passed the word to party officials and Bush political operatives to play down the presidential contest for now.
"They're telling people, 'Don't go with anybody, because that will bring on lame-duck status.' But the events of the day are bringing on lame-duck status faster than anything else," said a Republican who works in presidential campaigns and asked not to be identified because he is advising '08 hopefuls.
Other Republicans deny that there's a formal effort to keep the party establishment from shifting its energies to 2008.
"Obviously, everybody wants to keep the focus on what's going on in Congress this year. But I think most people, while kind of auditioning candidates, are really going to try to wait until after the election this November," said Robert Kjellander of Illinois, treasurer of the Republican National Committee.
For the first time in a contested nomination fight, the 168 RNC members will be automatic national convention delegates, making them an important early target for '08 candidates - the equivalent of "a large state," said Mike Duncan of Kentucky, an RNC member who will be among the activists at the biennial Southern Republican Leadership Conference, which ends Sunday.
The gathering features a presidential straw vote that home-stater Frist is expected to win.
"I'm sure that whoever gets the most votes will think that it means something," said Duncan, who chaired the event six years ago. But "I don't think there's a direct correlation between straw votes at this point and presidential nominees."