A recent CNN poll had a lot of eye-popping numbers. But one was particularly striking: 38 percent.

That's the number of self-identified Republicans who now put themselves down as against the Iraq war. This all sums up in stark terms the anxiety now causing palpitations in Republican hearts in Washington. Especially when you consider another number: 16, the number of months before the 2008 election.

Sen. Richard Lugar's (R-Ind.) comments demanding a change in course only heightened the pressure.

President Bush gives every indication that he intends to keep troop deployments at their current level through January 2009. Of course, if everyone chills out in Iraq and finally throws him the parade he has been holding out for, he'll begin bringing the troops home.

But on planet Earth it's stay the course, steady as she goes, through January 2009.

The president's ability to pull that off— both in terms of raw votes and public sentiment— rests almost entirely on a solid phalanx of support from congressional Republicans and 2008 Republican presidential aspirants. They don't have to be for the president's war exactly, or his conduct of it. But they need to stay resolutely opposed to Democratic efforts to end it. That's the key. As long as that's the case, as long as the vast majority of Republicans oppose Democratic attempts to end the war, that seems likely to keep Democrats from really going to the mat over it. As long as Democrats don't force a major confrontation, that keeps it all murky in the public mind who's for or against. And that keeps Republicans who are keeping the U.S. Army and Marines in Iraq against the wishes of the vast majority of the American people out of the public bull's-eye.

But eventually — maybe as soon as September — public opposition will become so overwhelming that the Democrats may be willing to really force the matter and not worry about lacking any bipartisan cover. Or maybe by September enough Republicans will see the numbers and give in and provide the Democrats their veto-proof majorities.

However it happens, whatever or whoever gives way first, the trend is unmistakable. And even if the Republicans can maintain unity and defy political gravity through 2008, they can see as well as anyone what will happen if they go into the 2008 election with sub-30 percent support on the defining issue of the day.

The key is that, for some liminal period over the next several months, there's still a paradoxical safety in numbers for Republicans sticking with the president. But no one wants to be the last one to the door. If you're a Republican congressman and you've been carrying the president's water on Iraq for years, you don't want to be on the losing side when Congress finally ends the war in spite of the president.

At that point, even if you flip-flop and start saying we've got to change course and try to get on the right side of public opinion, then you're probably just doubly screwed. And if it's mid-2008 when that happens, you're really not in a good place.

If you're a Republican member of Congress, would you rather go into the 2008 election still as a staunch supporter of the Iraq war or as a longstanding staunch supporter of the Iraq war who suddenly changed his or her position in June, 2008?

The truth is that the president is playing a high-stakes game of chicken with his fellow Republicans. He's driving a hundred miles an hour toward the cliff, way too fast for them to jump out of the car without risking serious injury. But as the cliff gets closer, they'll start to jump.