For the Democrats, who have a base of support that clearly wants out of Iraq, framing the issue in terms of Afghanistan makes it a lot easier, politically, to pull out of Iraq. But leaving Iraq will be no easy thing. Experts who side with Mr. McCain argue that a quick American exit from Iraq could lead to a conflagration in the Middle East that could end up involving Saudi Arabia and Iran in a Shia-Sunni-Kurd war  a conflict that would have few winners and would likely produce an enormous number of civilian casualties.

Beyond that, the logistics of pulling out 130,000 troops from Iraq would be daunting, and it could take close to a year to get all the equipment out. Indeed, some military experts say that if the United States military was given a year to exit Iraq, it would be so consumed with the logistics that it wouldn’t be able to do anything else.

Defense Secretary Robert Gates entered the fray earlier this month, for a moment sounding almost like the (gasp!) Clinton and Obama camps by urging Europeans to draw a distinction between the wars. During remarks on his way to Munich to take the Europeans to task for not sending enough troops to support NATO in Afghanistan, Mr. Gates said part of the problem was that many Europeans were conflating Iraq with Afghanistan.

“I worry that for many Europeans the missions in Iraq and Afghanistan are confused,” Mr. Gates said. “I think they combine the two.” It was an unusually candid acknowledgment from a senior member of the Bush administration that the war in Iraq had exacted a cost, in NATO’s chances for victory in Afghanistan. Many Europeans, Mr. Gates said, “have a problem with our involvement in Iraq and project that to Afghanistan, and do not understand the very different  for them  the very different kind of threat.”

The problem is, with the United States Army stretched thin in Iraq, the Bush administration has, thus far, been left to hector its NATO allies to send additional troops to handle the growing Taliban insurgency in Afghanistan. And European populations generally disapprove of their troops being sent into harm’s way in Afghanistan. No surprise, given the opposition on the streets of Europe to the American invasion of Iraq. That’s what Mr. Gates means when he says that Europeans conflate the two: Why help the United States in Afghanistan, the European logic goes, when America would be able to handle Afghanistan much more easily if its G.I.’s weren’t bogged down in Iraq?

In any case, the dynamics of the two conflicts are not the same, many foreign policy experts stress. The rapidly deteriorating situation on the Afghanistan/Pakistan border, the Musharraf government’s increased inability to confront Islamist insurgents in its border provinces, combined with the resurgent Taliban in Afghanistan have turned AfPak into America’s No. 1 national security problem, these experts say, even as parts of Iraq seem to have quieted since more American troops were sent there last year. Conditions in Pakistan became even more volatile on Monday after the party of President Pervez Musharraf suffered a drubbing in parliamentary elections, leading some to question how long Mr. Musharraf will be able to cling to power and how much of his already diminished authority he can retain. And Pakistan, the experts say, is inextricably linked to Afghanistan.

“Losing Afghanistan would be far more consequential than losing Iraq,” says Bruce Hoffman, a Georgetown University professor who was an adviser on counterterrorism to the Coalition Provisional Authority in Baghdad in 2004. “If Pakistan, especially along the border, fell into complete disarray, the integrity of the Afghan country and its government will be even more threatened, and that would have far greater repercussions for us.”