July 11 (Bloomberg) -- Former Tennessee Senator Fred Thompson, a champion of conservatives, and Rudy Giuliani, a favorite of political independents, may be the biggest beneficiaries if John McCain's bid for the Republican presidential nomination collapses, political experts say.

McCain's campaign is teetering after the loss yesterday of his chief political aides, a blow that comes the week after a disappointing fund-raising report. McCain, 70, once the Republican frontrunner, is vowing to fight on amid growing speculation about his viability.

If McCain is forced to abandon the race or loses more ground, Thompson and Giuliani will try to scoop up his political and financial backers.

``Those people who were attracted to McCain on the issues will go to Giuliani and those who were attracted by his perceived inevitability will probably now be attracted to Thompson,'' said David Keene, chairman of the American Conservative Union in Alexandria, Virginia.

In the latest USA Today/Gallup poll, Giuliani led with 30 percent backing from potential Republican primary voters; Thompson, an undeclared candidate, scored 20 percent and McCain 16 percent. Former Massachusetts Governor Mitt Romney received 9 percent in the July 6-8 survey.

The latest uproar in the McCain camp was triggered by the resignations of John Weaver, his senior strategist, and Terry Nelson, the campaign's manager. Rick Davis, chief executive officer of the campaign, was tapped to fill Nelson's duties.

Sounding Board

Weaver's departure stunned political observers because he has been a sounding board for the Arizonan for many years.

``This is a campaign organization that should have been hitting on all cylinders, not throwing off parts,'' said Peverill Squire, a political science professor at the University of Missouri in Columbia and an expert on Iowa politics. ``It is becoming harder and harder to concoct a scenario where McCain pulls out the nomination.''

Political professionals who reckon Giuliani, 63, will inherit much of McCain's support base that judgment on the former New York mayor's strong stand on terrorism and national security and his against-the-grain appeal to independents.

Those who say Thompson, 64, has the most to gain from a McCain crack-up consider Giuliani too out of step with the party's traditional values voters to reap much of a reward.

`Consistently Conservative'

``Thompson has already hurt McCain'' by siphoning off some of his backers, said Merle Black, a political scientist at Emory University in Atlanta. Black said traditional Republican voters may see Thompson as ``the more consistently conservative'' candidate in the field.

Thompson backers predict that if McCain is forced to drop out, the lion's share of his supporters, staff, and fundraisers will gravitate toward a presumed Thompson bid.

``There's a populist movement that is following Fred Thompson now,'' said Bob Davis, chairman of the Tennessee Republican Party. ``A lot of folks who probably supported McCain will probably be drawn to Senator Thompson for that very reason.''

While Romney is running fourth in national polls, he claims a frontrunner's mantle because he's ahead in Iowa and New Hampshire surveys. He says early successes in those states will make him a national force.

Romney had 25 percent in an American Research Group Inc. survey in June of likely Iowa caucus participants, with Giuliani second at 18 percent and McCain third with 13 percent. A June ARG poll of likely New Hampshire primary voters gave Romney 27 percent, with 21 percent for McCain and 19 percent for Giuliani.

Money Shortfall

Whit Ayres, a Republican pollster, said McCain's distress ``helps all the other top-tier contenders because one of the primary candidates is not going to have the money to compete in television or on organization.''

McCain's latest troubles began when the candidate, recently returned from a trip to Iraq, met with Weaver and Nelson to discuss campaign shortcomings on the money front, according to a campaign adviser who spoke directly with the duo.

In the discussions, it became clear that McCain had lost confidence in his team's fund-raising abilities, which led to offers of resignation that were accepted, the adviser said. Tensions came to a head when the issue of whether McCain would need to accept federal matching funds was raised.

That would have provided McCain some quick cash but would also limit his overall spending to about $50 million. Giuliani and Romney, 60, each have already raised more than $30 million and don't plan to accept public aid for the primary elections.

Iraq War

In a related move, top campaign aide Mark Salter, who is closer to McCain than any of his other campaign chieftains, agreed to become an unpaid senior adviser.

Asked about his recent presidential setbacks, McCain told reporters on Capitol Hill yesterday that he had no intention of abandoning his presidential quest. ``I'm very happy with the campaign,'' he said.

McCain's support for the Iraq war and for legislation creating a path to citizenship for illegal immigrants hurt him with donors in recent weeks. McCain has urged lawmakers to give the administration's troop-increase plan a chance.

``No lasting political settlement can grow out of U.S. withdrawal,'' McCain said. While senators may be tired of the war, ``we cannot let fatigue dictate our policies,'' he said.

To contact the reporter on this story: Heidi Przybyla in Washington at hprzybyla@bloomberg.net

Last Updated: July 11, 2007 08:49 EDT