Hardly a competitive Republican in a House or Senate race this year hasn't enjoyed the fundraising prowess and personal gravitas of Arizona Sen. John McCain.

McCain has been crisscrossing the states to stump for GOP hopefuls and sending out his red-hot signature on fundraising solicitations for needful candidates.

While the four-term senator says he's undecided about his presidential prospects, political analysts say no non-candidate would task himself with such a schedule if he didn't have higher ambitions. They also agree that the popular maverick leads the pack of Republican 2008 White House contenders if not on the sheer breadth of his fundraising operation alone.

Editor's note: This is the second in a two-part series on prospective presidential candidates in 2008. Click here for the first article on Democrats.

Fundraising for the party, spreading the wealth around so that he can call in the chits later, is a strategy at which McCain is excelling. But McCain is not the only one; Massachusetts Gov. Mitt Romney has been raising funds for candidates all over the map, and to a lesser extent, so have former New York Mayor Rudolph Giuliani and Virginia Sen. George Allen.

While they may be coy about their political intentions, these men comprise the current top tier of hopefuls a year-and-a-half ahead of the wide-open GOP primaries.

"I kind of like to call this 'the exhibition season.' The candidates are doing everything they can to show they are real contenders," said Sean Evans, a political science professor at Tennessee's Union University. "John McCain appears to be the frontrunner at this point."

Dominating the fundraising landscape may not reflect public opinion, and early polling shows that McCain will have hefty competition in the Republican primaries, which typically draw dedicated conservative grassroots voters.

Still, he is at or near the top of many surveys of preferred GOP candidates. In an August Pew Research Center for the People & the Press poll, for example, McCain won 26 percent of support among 1,219 registered voters nationwide, including 409 Republicans. That put him ahead of Giuliani by two points, with Secretary of State Condoleezza Rice in third place at 18 points. Rice has repeatedly said she has no interest in running for president.

McCain, who lost the presidential nomination in 2000 to George W. Bush, has been a hawk on defense issues but more moderate on social ones. He spearheaded the 2002 campaign finance reform law, not a favorite of conservatives; wrote immigration reform legislation with Democratic Sen. Ted Kennedy that many say amounts to amnesty for illegals; and recently worked with Democrats in the Senate to avoid a filibuster over President Bush's judicial nominees. To conservatives, he's a mixed bag at best, and at worst "not one of them."

"This might be a challenge," said Alvin Williams, president of the conservative Black America's Political Action Committee. "It looks like he's trying to address [conservative concerns] … trying to tap into a conservative base of voters. He seems like he's definitely taken a page or two from Bush's playbook, making contracts and reaching out."

But Richard Viguerie, longtime conservative activist and author of the recently released "Conservatives Betrayed," said those kind of tactics tricked conservatives into thinking Bush was one them in 2000.

"At this time, none of the candidates being mentioned is worth our conservative support," Viguerie said. "I'd rather conservatives sit out the election than support one more establishment candidate who abandons them and moves left."

McCain appears to be concerned about sentiments like this. His falling-out with social conservatives, particularly in the South, was considered key to his losing the 2000 nomination, though many have blamed Bush's campaign operatives for engaging in a smear campaign against McCain ahead of the critical South Carolina primary.

Nonetheless, McCain has since made nice with Bush and is pursuing conservative support, sometimes at the dismay of his more independent, moderate fans. He raised eyebrows, for example, when he gave the graduation address at Rev. Jerry Falwell's Liberty University in May.

So far, say analysts, McCain seems to be striking the right balance, winning over many of the big Bush donors who contributed to the president's very successful fundraising apparatus since his time as governor in Texas.

Being a decorated war veteran and member of the Senate Armed Services Committee also can't hurt. McCain has stuck with the president on the rationale for staying in Iraq, but hasn’t been afraid to criticize Secretary of Defense Donald H. Rumsfeld.

"Many believe that if he can win the nomination, he can definitely win the general election," said Chuck Muth, a libertarian-minded Republican and president of Citizen Outreach, a public policy think tank in Washington, D.C. Muth said McCain certainly has cross-over appeal.

"He doesn't scare Democrats, he's not a hard-core conservative. He's not perceived as a right-wing Republican," he said.

But if McCain is playing the field, winning over many of the right contacts, Romney is not far behind. In Massachusetts, which Republicans love to hate for its predominantly liberal politics, Romney, a conservative Mormon, is making headlines for his own hard-charging campaign.

"He's getting a lot of ink because of the money he's raising and the people he is hiring," Evans said.

Romney, the current chairman of the influential Republican Governors Association, is known for bucking the liberal social trend in his state, most notably on gay marriage. At the same time, he is experimenting in Democratic territory with universal health care in his state. Romney argues the fiscal logic, saying it makes more sense to pay for preventive care before uninsured low-income residents face more expensive hospital bills.

"He is the one who is surprising people and has basically bolstered himself to be the main conservative rival to McCain," said Evans.

Washington conservatives also seem to gravitate toward Allen, who is busy fending off challenger Jim Webb for re-election to the Senate this November. A former Virginia governor, Allen hasn't said whether he is planning a run for president. A loyal Senate ally to Bush, he is someone who many conservatives hope can resurrect their principles in the White House, say election watchers.

"Right now, he seems to be the Goldwater, the hope of the conservatives," said John Gizzi, political editor of the conservative Human Events magazine, referring to conservative hero, Sen. Barry Goldwater, who lost to Lyndon B. Johnson in 1964.

"I think he is very popular with the conservative base of the party as well as the moderate wing as well," said Williams. "But it's not a giveaway — he's going to have to compete quite vigorously for it."

Allen made some unwanted headlines recently when he was forced to answer for remarks made about a young Webb volunteer who was videotaping the senator at a campaign speech in southern Virginia. Allen referred to the volunteer, an American citizen of Indian descent, as "macaca," which has been used in Europe as a racial slur, but which Allen says he did not intend.

Allen apologized but political analysts are saying time will tell whether the incident has any impact on his electoral prospects.

Then there is Giuliani, a former federal prosecutor and mayor of New York City whose response to the Sept. 11, 2001, terror attacks won him national praise and the label of Time magazine's Person of the Year. He has become a folk hero to Republicans, many of whom believe he has presidential potential.

Though he has not announced any intentions of running for president, Giuliani has been fundraising and speaking on behalf of candidates, and has made forays into the early voting states of Iowa and New Hampshire.

"Being the hero of 9/11, it has stayed with him for far longer than I would have thought," Gizzi said. "In states you wouldn’t think he would be a draw, like North Carolina, he is a major hit."

"The Iowa numbers seem to say that the sheen of 9/11 and the roll that Rudy Giuliani played has not warn off," said Weekly Standard editor Fred Barnes.

Giuliani has been reaching out to conservatives, seemingly aware that his liberal positions on social issues, like homosexuality and abortion, are likely to work against him with the base. Some say he might have reached out too far — fundraising for former Christian Coalition director Ralph Reed in his recent bid for Georgia lieutenant governor. Reed lost the primary, in part because of his ties to convicted lobbyist Jack Abramoff.

But Barnes said crowds in North and South Carolina have been surprisingly enthusiastic for Giuliani.

"These are the states that are supposed to be trouble for Giuliani because he's very liberal on social issues. But a lot of conservatives, well not a lot, some, at any rate, have come to the conclusion that look, the big issue is going to be national security, protecting the country and leadership, and those are the things that Rudy Giuliani is strong on," Barnes said.

"I've seen [Giuliani] speak before, he's very much a charismatic speaker ... and in a time when national security and terrorism are important, he stands for order," Gizzi said. "But, if you remove 9/11 and the issues of crime, you will find a very liberal Republican … I don’t think that is going to play with conservatives."

Conservatives may not go for Senate Majority Leader Bill Frist either. Frist is retiring from his Senate seat this year. The two-termer from Tennessee has been putting out the feelers for higher office for some time, even joining other wannabes this August at the Iowa State Fair, sacred ground for any presidential prospect.

But Republicans, particularly incumbents, aren't very popular these days, and have been blamed on both sides of the political fence for getting little done in Congress amid the partisan bickering in Washington. Frist has been called ineffective by his detractors, a sentiment that has done nothing to brighten his prospects for the White House, say observers.

Others say while Frist may be perfect senator material, he may not have what it takes to win a presidential horse race.

"Bill Frist has surprised people with the money he has raised and [the supporters] who have gotten behind him," Evans said. "But most people are still not convinced about his appeal to voters. I've met Frist before, he's excellent in a one-on-one conversation, but you put him in front of a group and he needs a lot of help.

"I'm not sure he would be able to develop a style that would allow him to connect with enough people to be successful," he added.

Also in the loop is former House Speaker Newt Gingrich, who draws a respectable third or fourth place in most polls. That's not bad, especially since he has been out of office for eight years, spending much of his time on the pundit circuit.

But being that history says that nominees for the White House are very different from the leadership two years earlier, it is hard to gauge whether this group of top-tier candidates will be yesterday's news two years from now, say analysts.

"I think it is an unsettled environment," said Terry Madonna, public affairs professor and head of the Keystone Poll at Franklin and Marshall College in Pennsylvania. While McCain appears to be a strong frontrunner, the Republican primary is still wide open. "We could have a genuine surprise."