The 2008 presidential race could pair a Democratic senator who has been backing away from the Iraq War against a Republican senator who still wants more U.S. troops to enter the battle.
And while New York Sen. Hillary Rodham Clinton, the Democratic front-runner, has so far borne more criticism for her Iraq stance, pundits say the Republican front-runner Arizona Sen. John McCain could end up with much more explaining to do.
"John McCain is a very attractive candidate in many ways, but going into 2008, Iraq may be a nonstarter for him," said Dominic Tierney, a political scientist at Swarthmore College. "It may be the reason he loses to Hillary or Barack Obama."
For McCain, the problem is that independent voters, who have long found him an appealing candidate, are turning against the war but he isn't.
A Gallup/USA Today poll last week found that, by nearly a 2-1 ratio, independents oppose sending more U.S. troops to Iraq.
But McCain who has been arguing for a larger U.S. fighting force in Iraq for years stood behind President Bush's plan to add 21,500 troops to the U.S. fighting force in Iraq. And during a Senate Armed Services Committee hearing Friday, he warned against a quick "surge" in troop levels followed by a withdrawal.
"As I have said before, a small, short surge would be the worse of all worlds," McCain said.
"We need troops in the numbers required to do the job in place for as long as it takes to complete their mission. . . . It would be far better to have too many reinforcements in Iraq than to suffer once again the tragic results of insufficient force levels."
Such comments are the kind of muscular foreign policy McCain has always advocated. And that fact might provide him some political insurance in his 2008 presidential race.
"Right from the start, he's been saying more troops are needed, and a lot of people think there's a lot of wisdom in that," said Tierney, author of "Failing to Win: Perceptions of Success and Failure in International Politics."
McCain's hawkishness, combined with his experience as a Vietnam War hero, should appeal to traditional Republican voters who draw a hard line on foreign policy, said John Mueller, a political scientist at Ohio State University who studies the politics of national security issues.
"His foreign policy is to go after everybody west of Iceland," Mueller said.
Political pros said McCain's war stance is unlikely to hurt him in the Republican primaries, where his key challengers at this point, former New York Mayor Rudolph W. Giuliani and former Massachusetts Gov. Mitt Romney, also support Bush's plan. But if McCain emerges as the GOP nominee, that's where his Iraq troubles could begin.
If U.S. troops don't come home in the next year, "it's going to be bad for him," Mueller said.
Meanwhile, Clinton faces exactly the opposite problem. Political scientists said she could end up facing two serious primary challengers Obama, a first-term senator from Illinois, and former Sen. John Edwards of North Carolina who are more in tune with the party's liberal base on the war issue.
Clinton has been increasingly critical of the war effort in recent months and has been calling for a slow withdrawal of U.S. forces to pressure the Iraqi government to take control of its own country.
"That would really demonstrate to the Iraqis that we don't have an open-ended commitment," she told ABC News on Saturday while on a daylong visit to Iraq.
"We are not going to be here providing protection for their leaders, which we do. We are not going to be here standing by and trying to be called in from time to time as they see fit. That is not in the cards."
Despite such critical comments, Clinton, in contrast to Edwards, has never repudiated her 2002 vote giving Bush the power to invade Iraq.
Obama, meanwhile, has the advantage of having opposed the now unpopular war from its start.
"[Clinton's] opponents can say: Can you trust her, in terms of competence? She was wrong about the war," said Susan MacManus, a political scientist at the University of South Florida.
But if Clinton manages to maneuver her way through the primaries, her war stance might help her in the general election.
For one thing, MacManus noted that the general electorate tends to be more centrist on matters of war and peace than many Democratic voters. That means the voters in the November 2008 election may be more in tune with Clinton than they would be with her Democratic opponents. For another, if Clinton ends up facing McCain or another hawkish Republican and if U.S. troops are still fighting a brutal war in Iraq 18 months from now -- the GOP candidate will be bearing the brunt of the criticism.
"All Hillary has to do is keep quiet about her plan" to end the war, Tierney said.
That's what GOP presidential nominee Richard M. Nixon did in 1968 in the midst of the unpopular Vietnam War, and he won that election.
Of course, political pros warn that it is far too soon to accurately predict the politics of the 2008 presidential race. And they all say McCain possesses extraordinary strengths as a presidential candidate, most notably his reputation for integrity and straight talk.
Nevertheless, even McCain acknowledges that his reputation might not be enough to get him elected president in the midst of an unpopular war that he continues to support.
On the night that Bush unveiled his plan to send more troops to Iraq, McCain told CNN's Larry King: "I would much rather lose an election than lose a war."