WASHINGTON – Election Day is more than a year away, but Republican Sen. Susan Collins of Maine is facing a barrage of attack ads, protesters at her local offices and a strong Democratic challenger.

It’s a far different environment from her last race for re-election, when her popularity was soaring and she won a commanding 58 percent of the vote.

The one-word explanation for the change: Iraq.

As Congress wrestles with Democratic proposals to withdraw U.S. troops and limit the war in Iraq, the home-state pressure on Collins and other Republicans helps explain why an increasing number of GOP lawmakers seem ready to veer from the party line.

The 2008 campaign season is beginning to take shape for congressional candidates, and many Republicans see warning signs that the steepest price for President Bush’s Iraq policy might be paid not by the president, who will not be on the ballot, but by the GOP lawmakers who will be.

In New Hampshire, a recent poll found Republican Sen. John Sununu trailing one possible Democratic challenger by a double-digit margin.

In Minnesota, Sen. Norm Coleman raised about $300,000 less in the second quarter than his best-known Democratic challenger, comedian Al Franken.

In Oregon, approval ratings for Sen. Gordon Smith did not improve after he switched positions and called for a U.S. troop withdrawal.

Republicans say they hope passions about the Iraq war will cool by the time 2008 ballots are cast. But they acknowledge that if the election were held tomorrow, the war would be a ball and chain around the GOP ankle.

In Maine, the attacks on Collins have come early and often.

They began when a group of anti-war Iraq veterans aired an ad during the February Super Bowl urging Collins to oppose Bush’s proposal to increase U.S. troop strength. The ad, playing on the theme of “on the one hand and the other hand,” featured an Iraq war veteran who was missing one hand.

A later ad linking Collins with Bush’s Iraq policy was so withering that the Collins campaign filmed an Internet video response, crying foul on the facts and pointing out that it came from a national political group.

“No Maine-based group funded this attack,” her response said.

Her opponents still have work to do. Early polls show that Collins’ approval ratings are still high and that she has a solid lead over her Democratic challenger, Rep. Tom Allen.

Still, Jennifer Duffy, analyst of Senate races for the nonpartisan Cook Political Report, sees signs that Collins is on guard. “I’ve never seen her so active so early,” said Duffy, who has rated Collins as among the most vulnerable Senate Republican incumbents.

Allen, her challenger, entered the race early and has focused heavily on the fact that he voted against the 2002 resolution authorizing the Iraq war, while Collins voted for it. While Collins has criticized Bush’s Iraq policy of late, Allen says Collins is all talk and no action, because she has not supported a withdrawal deadline.

She recently has come under additional political pressure to do so, because the other Republican senator from Maine, Olympia Snowe, endorsed a withdrawal deadline.

Steve Abbott, Collins’ chief of staff, forecast she would weather the anti-war attacks, because her constituents know her and trust her judgment. “They have made up their minds about her, and they like her,” he said.

The party was hobbled by anti-war sentiment in the 2006 midterm elections, when Republicans lost control of Congress. If the politics of the war do not change, Republicans fear their hope of regaining control of Congress in 2008 will not be realized.

“Do we hope Iraq is not an issue by Election Day? Sure,” said Rebecca Fisher, spokeswoman for the National Republican Senatorial Committee. “But can we guess where we will be next year? No way.”

The political fallout from the Iraq debate is hard to gauge, analysts say, because it will hinge in large part on uncertain developments in the war and whether Bush changes course.

That is why more Republican senators, after standing by Bush for years, now are trying to reshape policy well before Election Day arrives. Last week’s Senate debate on defense policy featured a who’s who of Republicans facing re-election in 2008 signing on to proposals designed to signal their dissatisfaction with the course of the war.

Collins, Sununu and Coleman joined Sens. Lamar Alexander, R-Tenn., and Pete V. Domenici, R-N.M., in backing an amendment that would set a target but not a binding date for withdrawal of U.S. troops from Iraq – a recommendation of last year’s bipartisan Iraq Study Group.

The fact that so few Republicans have been willing so far to embrace that firm deadline means they will continue to be exposed to criticism from Democrats and from constituents weary of the war. Some Republican strategists worry that no matter what lawmakers do now, the issue will leave some Republican incumbents vulnerable.

“There will be races that will be more competitive in places you don’t expect,” said a senior adviser to one Republican facing an unusually tough re-election contest. “Fifteen months is a lifetime in politics, it’s true. But questions like this war don’t go away quickly. This has been three years coming. I don’t think it goes away in a New York minute.”