Republican presidential hopefuls, from left, Rep. Tom Tancredo, R-Colo.; former secretary of Health and Human Services Tommy Thompson; Sen. Sam Brownback R-Kan.; former Massachusetts Gov. Mitt Romney; former New York City Mayor Rudy Giuliani; Sen. John McCain, R-Ariz.; former Arkansas Gov. Mike Huckabee; Rep. Duncan Hunter, R-Calif.; former Virginia Gov. Jim Gilmore; and Rep. Ron Paul, R-Texas, appear on stage Tuesday before the Republican presidential primary debate put on by St. Anselm College in Manchester, N.H.

MANCHESTER, N.H. ? Republican presidential candidates wrestled with issues of war, God and science in a freewheeling two-hour debate Tuesday night, at times battling over which of them are conservative enough for the party’s primary voters while still sufficiently distant from a GOP president suffering low approval ratings.

The leading candidates refused to second-guess President Bush on the decision to go to war in Iraq or to criticize the administration’s decision to open talks with Iran.

But only Sen. John McCain of Arizona offered a defense of the Bush-backed plan to reform U.S. immigration law, an increasingly critical issue for the Republican base.

And the field of candidates came up with generally unenthusiastic answers to a question about the public role Bush should play after he leaves office, with U.S. Rep. Tom Tancredo of Colorado going so far as to suggest that he would ask the sitting Republican president not to “darken the doorstep” if Tancredo is ever in the Oval Office.

All of the Republicans agreed that gays and lesbians should not be allowed to serve openly in the military and that English should be the official language of the U.S.

Former Massachusetts Gov. Mitt Romney professed his faith in Jesus Christ as his savior and pledged not to step away from his Mormon religion while claiming that some “pundits” think it might help him politically. And three of the candidates explained how they can believe in the biblical story of creation while not explicitly rejecting the Darwinian theory of evolution.

Amid lengthy discourse about the role of faith and God in politics, a summer storm raging outside the debate hall turned especially violent – at one point completely cutting off the microphone as former New York Mayor Rudy Giuliani was trying to explain his views on abortion.

“Look, for someone who went to parochial schools all his life, this is a very frightening thing that’s happening right now,” Giuliani joked.

The spirited exchanges took place in what was the third debate for the field of 10 Republicans, gathered in the early primary state traditionally so influential in helping both parties to choose their presidential nominees. With recent polls showing the moderate Giuliani leading the field of Republican candidates, followed most closely by McCain and Romney, the other candidates were clearly out to prove their own credentials to the GOP conservatives likely to help tip the balance.

But there has been simmering dissatisfaction among conservatives in the party, with the social positions of some of their candidates and skepticism that any of them have the charisma and power to win in a head-to-head match up with a Democrat. As a result, a notable presence looming over Tuesday night’s event was that of former U.S. Sen. Fred Thompson of Tennessee, who has made it all but official that he will get into the race for the GOP nomination, perhaps as early as this summer.

Thompson’s proximity on Tuesday night was literal as well as figurative. Going into the event, declared candidates were aware that the actor-turned-senator-turned-actor was on deck for a Fox News interview immediately following the debate.

“More and more I wish that I had the opportunity to do the things that only a president can do,” he said. “And I think we’re coming at a time of a crossroads in our country in many respects.”