Okay, Matt: here ‘goes.
Hillary Clinton’s foreign policy would be precisely the same as Tony Blair’s. (Indeed, Hillary Clinton as President would in most ways be precisely the same as Tony Blair.) She will be confrontational towards Iran, will not withdraw from Iraq, will be unsuccessful at wooing Europe to her way of seeing things. She’ll be relatively tougher on China and Mexico than people expect. She would not withdraw from Iraq. She would not join Kyoto.
Barack Obama’s foreign policy would be a somewhat left-tilted version of George H. W. Bush’s realism: conciliatory towards China and Mexico, pro-free-trade, highly engaged in the Israeli-Palestinian conflict, but more interventionist than people expect generally and in the Middle East specifically. He would attempt to shepherd the partition of Iraq. He would not join Kyoto. Whether he would be effective is another matter; we have very little to go on in that regard.
John Edwards’ foreign policy is an academic question as he will never be nominated. If the inconceivable happens, his foreign policy will be an ineffectual mish-mash of contradictory impulses reminiscent of the Carter Administration.
Al Gore’s foreign policy is also academic as he will not run, but on the off-chance that I am wrong, it would be strikingly similar to Barack Obama’s as described above, except that he would join Kyoto.
Rudy Giuliani’s foreign policy would be precisely the same as George Bush’s. (Indeed, apart from judicial appointments and some other staffing issues that matter a lot to the Christian Right, and apart from the major difference that Rudy will have no Dick Cheney, a Giuliani Administration would be strikingly similar to the current President’s.)
John McCain’s foreign policy would be the most unpredictable of all the candidates. I would anticipate at least one, and possibly multiple "hail Mary" gambits. I would not be at all shocked if McCain attempted a serious rapprochement with Iran. I would also not be shocked if McCain got us into a war with China. I would also not be shocked if McCain tried to get us into Kyoto (though I would be shocked if he succeeded). I would, however, be shocked if McCain withdrew from Iraq. But, then again, that’s why he would lose in a general election.
Mitt Romney’s foreign policy is an academic question as he will never win a general election even if he manages to get nominated. If the inconceivable happens, his foreign policy would be essentially the same as Condoleeza Rice’s. (That’s not exactly an insult, but it certainly isn’t a compliment.)
Fred Thompson’s putative foreign policy is an interesting question. Thompson, if elected, will come in with a set of hawkish advisors and hawkish instincts, but without the itch to act decisively that has been the hallmark of the President, or the paranoia that has been the hallmark of the Vice President. I would expect him, as a basically lazy man, to be pretty manipulable by his advisors. But it’s not so clear to me that he will let them maneuver him into actually doing anything. I guess I would say that I expect a Thompson foreign policy – and a Thompson Administration - would resemble Reagan’s . . . except without a driving purpose and theme. Which kind of doesn’t make sense. Anyhow, he’ll be conciliatory towards China, more aggressive towards Mexico, rhetorically supportive of Israel and hostile to Iran, but I’m not sure how much any of this will translate into actual action.
In general, I think it’s more important to pay attention to the candidate’s character, who the candidates advisors are, and how the candidate selects and uses these advisors, than it is to listen to what policies they actually propose. Because first, those proposals are all provisional (everything looks different once you’re actually sitting in the President’s chair), and, second, because the world will throw up unpredictable challenges, and the President’s reactions will not be the result of long study: they will be instinctive, based on personality and past experience.