Congressional Democrats seldom agonize before ditching presidents of their own party. In 1967, they fled Lyndon B. Johnson right and left -- the right over civil rights, the left over Vietnam. A decade later, they shoved Jimmy Carter's legislative agenda back in his face. Bill Clinton faced constant rebellion from his own side.

Republicans are made of firmer stuff. They value loyalty, hierarchy and deference over independence and private conscience. When the GOP controls the White House, the party's congressional wing readily accepts its subordinate position. For an example of widespread GOP abandonment of a president of its own party, you have to go back to Watergate, when, as now, Republican legislators faced a tricky calculation about how to handle an embattled, isolated and failing president.

For the legislators of today, this problem is largely framed in terms of Bush's proposal to send 21,500 additional soldiers to Iraq. In the next few weeks, the House and the Senate will take up resolutions opposing the "surge." Though these measures will be non-binding, they will amount to a no-confidence test for the Bush presidency. Losing his own party's support on the war would be an unprecedented repudiation, marking the end of Bush's ability to govern or lead. If you are a House or Senate Republican, how do you decide whether to join the dissidents or stick with Bush?

Should you happen to be a moderate, or from the Northeast, or facing a tough re-election campaign in 2008, the imperative is clear: Abandon ship. As even his bitter-enders acknowledge, Bush's Iraq policy just cost the GOP control of Congress. And the 2008 election, when 22 of the 34 open Senate seats will belong to Republicans, could make 2006 look like a picnic. Those already reaching for life vests include such vulnerable purple-state incumbents as Norm Coleman of Minnesota, Gordon Smith of Oregon and Susan Collins of Maine.

If you're a Republican running for president rather than for re-election, the decision about backing Bush is different. It's about the views of conservative primary voters, not swing voters in a general election. This explains why the three candidates who face the most conservative skepticism -- Sen. John McCain of Arizona, former New York Mayor Rudolph Giuliani and former Massachusetts Gov. Mitt Romney -- have all opted to endorse the surge idea.

Simple consistency

For McCain, it may be a matter of simple consistency. Given his hawkish views to date, it would be preposterous for him to turn against the Iraq war now. Romney, who is attempting to be the favorite Mormon son of the party's Christian evangelical base, wants even less daylight between himself and those on Karl Rove's speed dial. Giuliani, for his part, realizes that a Republican moderate cannot also be a Republican maverick. His support for the surge says to the conservative gatekeepers that while he's not exactly one of them, he is emphatically not what they most dislike: a preening press hound looking to strike a noble pose.

There are two conservative presidential hopefuls, Sam Brownback of Kansas and Chuck Hagel of Nebraska, who have come out against Bush's surge. Their political calculus is more complicated still. Both Brownback and Hagel are second-tier candidates with limited national visibility. Their presidential opportunity arises only if those in the first tier falter. Thus, they need to differentiate themselves as strongly as possible. Brownback is positioning himself as the right wing's surge skeptic in case Romney's hawkishness proves untenable. Hagel, who has long been cast in the vexed role of understudy to the Senate's leading maverick, is clearly sick of walking in McCain's shadow. This is not to discount the sincerity of Hagel's opposition to the war. When he says the president's new plan "represents the most dangerous foreign-policy blunder in this country since Vietnam," he speaks as a wounded, decorated veteran -- just as McCain does when he supports Bush.

The GOP's wrath

Many congressional Republicans who are not running for president probably share Hagel's anti-war views, but fear the wrath of the party's disciplinarians if they speak out. An object lesson was recently provided by Jeff Flake, a GOP congressman from Arizona who lost a coveted Judiciary Committee seat as punishment for siding with the Democrats on a reform vote against "earmarks." Johnny-come-lately doubters also face the problem of explaining why they're changing their minds after supporting Bush's war for the past four years. For most of them, the safest course is to sound skeptical without crossing Bush directly, while hoping that Democrats miscalculate by trying to cut off funding to the troops.

Finally, there are those who face a simple imperative. Senate Minority Leader Mitch McConnell of Kentucky last week called Bush's surge speech "courageous and correct." House Minority Leader John Boehner of Ohio says the plan offers "our best shot at victory in Iraq." It doesn't much matter if they really think so. If your job is to keep order on a sinking ship, you can't very well run for the lifeboats yourself. We saw these types during Watergate as well -- Bush's father, then chairman of the Republican National Committee, was one of them. The greatest was the comically loyal Earl Landgrebe, a now forgotten Indiana congressman. "Don't confuse me with the facts," Landgrebe said the day before Nixon resigned. "I'm going to stick with my president even if he and I have to be taken out of this building and shot." That remains the default Republican position. It's going to be sorely tested in the months ahead.
JACOB WEISBERG is editor of Slate and co-author, with Robert E. Rubin, of "In An Uncertain World."

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