As differences over the Iraq War continue to bedevil President Bush and Congressional Republicans, the debate threatens to fracture the relationship between conservative activists and Republican Senators headed for tough re-election battles in 2008.

A prominent conservative radio talk show host recently has taken to the airwaves and the Internet, urging the National Republican Senatorial Committee to refrain from making money available to GOP Senators who vote to condemn Bush’s Iraq War policy.

“The NRSC Pledge,” created by Republican-friendly radio talker and blogger Hugh Hewitt — and championed by a collection of his online colleagues — is urging Republican activists to withhold contributions to the NRSC unless Chairman John Ensign (Nev.) promises to keep donations away from incumbents who vote against Bush’s proposed troop surge.

The Web site — www.thenrscpledge.com — boasted around 30,000 signers as of Monday, and that’s a cause of concern for Senate Republicans.

NRSC spokeswoman Rebecca Fisher said Monday the committee is taking Hewitt’s effort seriously, indicating the NRSC is concerned about the practical implications it might have on fundraising and grass-roots support for GOP Senate candidates.

“Of course we worry about the effect something like this has on online fundraising,” Fisher said. “As we explore different methods of fundraising, we have to be sure that we can effectively take advantage of every available avenue. And with a response like this blog has received, we take notice.”

Ensign, in an interview late last week on Hewitt’s nationally syndicated radio show, sounded sympathetic to the concerns of the pledge signers and vowed not to personally support any resolution critical of Bush’s plan to send an additional 21,500 soldiers to Iraq.

But the Senator declined to cave in to the pledge signers’ demands, saying his job as NRSC chairman is to elect as many Republicans to the Senate as possible.

Fresh off an election cycle that saw the NRSC come under pressure from conservatives over its staunch backing of then-Sen. Lincoln Chafee (R-R.I.) — who was so moderate he did not vote for Bush in the 2004 presidential election — Ensign and his team at the committee have worked to strengthen the NRSC’s ties to the GOP base.

Hewitt, who drafted the pledge and worked with another blogger to post it online, said in an e-mail interview Monday that he believes the GOP must serve as a “big tent” that allows differing viewpoints, as that is crucial to the party’s hopes of reclaiming majority status. But, Hewitt said, Iraq is not an issue on which Republicans can be flexible.

“The war is not an issue on which you can live to fight another day,” he said. “It is a life-or-death issue, and needs to be treated as such by Republican Senators. Some Senators might indeed suffer from a ‘no’ vote. But if a ‘no’ vote is the right vote in terms of national security, they should have the courage to make it.”

Hewitt’s criticism is significant, because his Web site is one of many widely read center-right blogs that were heavily involved in encouraging donations to the NRSC in the 2002, 2004 and 2006 cycles — though due to the committee’s support for Chafee, some bloggers, including Hewitt, urged Republicans to refrain from giving to the NRSC last year.

One former Republican Senate strategist with knowledge of what the NRSC went through with Chafee in the previous cycle said the pledge could trip up the committee’s efforts in 2008, though it is hard to project or quantify how much. Even if the pledge does little practical damage and its effects are limited to bad publicity among conservatives, it still could prove detrimental to Ensign’s push to reclaim the majority for Senate Republicans.

“When you have infighting, not only does it hurt from a dollars and cents standpoint, it hurts your ability to fight the opposition,” this strategist said. “Lots of time was wasted fighting that element last cycle, while the other side was focused on beating us.”

In less than a week, the pledge has gained traction among some influential center-right bloggers, threatening to create a rift between the GOP base and the NRSC at a time when Republicans are defending 21 Senate seats, compared with only 12 for the Democrats.

Among the 21 seats that are up, there are at least six that could prove to be competitive, depending on several factors, including the NRSC’s ability to hold down retirements. Raising enough money to compete with a Democratic Senatorial Campaign Committee that significantly outraised the NRSC in the previous cycle — and doing so in a presidential cycle when campaign contributions will be harder to come by — is seen as a key component of Ensign’s ability to turn things around.

Some GOP Senators facing potentially tough re-election bids — such as Sens. Norm Coleman (Minn.), Gordon Smith (Ore.), Susan Collins (Maine) and John Sununu (N.H.) — are running in Democratic-leaning states. They could face voter backlash next year if they don’t support some sort of Senate resolution opposing the Bush plan.

But Hewitt stressed that they’re not likely to win re-election in blue states absent strong support from conservatives.

The pledge reads:

“If the United States Senate passes a resolution, non-binding or otherwise, that criticizes the commitment of additional troops to Iraq that General Petraeus has asked for and that the president has pledged, and if the Senate does so after the testimony of General Petraeus on January 23 that such a resolution will be an encouragement to the enemy, I will not contribute to any Republican senator who voted for the resolution.

“Further,” the Pledge continues, “if any Republican senator who votes for such a resolution is a candidate for re-election in 2008, I will not contribute to the National Republican Senatorial Committee unless the Chairman of that Committee, Senator Ensign, commits in writing that none of the funds of the NRSC will go to support the re-election of any senator supporting the non-binding resolution.”

While Senators are negotiating over what the various anti-surge resolutions will say, Hewitt was keeping up the pressure at his Web site, www.hughhewitt.com, throughout the weekend and all day Monday.

In particular, Hewitt has been encouraging readers of his site to place telephone calls against a cloture vote to the offices of Republican Senate leaders and some of the GOP Senators seen as vulnerable next year and inclined to support a resolution if one comes to a vote.

However, support for the pledge is not unanimous in the conservative Internet community, with John Hawkins at www.rightwingnews.com arguing against it. Hawkins said the pledge could cost the NRSC on the fundraising front and lead to the defeat of conservative Republican Senators in 2008.

Hawkins praised Ensign for resisting the demands of the pledge signers, explaining that if the chairman was rolled on this issue, several new pledges motivated by strong feelings on other contentious matters likely would pop up. He also noted that the committee exists solely to re-elect incumbent Republicans, saying pressure could have — and should have — been brought to bear on those Senators who support the pending Iraq War resolution without involving the NRSC.

“That’s the reason the pledge is a bad idea: It puts the NRSC (in) a no win situation,” Hawkins wrote on his blog Friday. “They cannot possibly give people what they want, no matter how many people sign the petition.”