I believe there's a looming battle in the Republican Party over what America's role in the world should be, and the Iraq war spending bill may very well bring this fight out into the open in a matter of months, if not weeks.

From my point of view, and it is a view shared by many conservatives who e-mail and call me, none of the GOP presidential candidates is offering a coherent, thoughtful, philosophical explanation of what the future of U.S. foreign policy ought to be. To say we must fight terrorism isn't enough. It's too nebulous.

Today, Mitt Romney's campaign launched a new ad in which the former Massachusetts governor suggests now is not the time for America to "shrink from conservative principles" but rather to "stand in strength" so that we might remain "the world's military superpower." How, you ask? By rebuilding our military and leading a "great coalition of strength." For whom? "For our families, for our future, for America."

It really doesn't take much convincing to suggest to a conservative that the U.S. should increase the size of the military and spend more money on defense. Done and done. What the GOP is beginning to ask is, to what end? And this is where I see the party showing signs of stress fractures.

In a speech on May 1 to the U.S. Central Command, the president laid out, perhaps more coherently than ever, his rationale for continuing the war in Iraq:

"The goal of this new strategy is to help the Iraqis secure their capital, so they can make progress toward reconciliation, and build a free nation that respects the rights of its people, upholds the rule of law, and fights extremists and radicals and killers alongside the United States in this war on terror."

To an increasing number of Republicans, that description sounds like an academic exercise, doomed on many levels.

"Secure the capital." Seems like a fine military goal. Let's do it.

"Reconciliation." Historically unlikely.

"Respects the rights of its people." Religiously challenging.

"Fights extremists and radicals alongside the United States in this war on terror." Increasingly unthinkable.

And so many in the GOP are looking at the first goal as the only goal. Security first. Security only. The war at home is just heating up.