How would U.S. policy on Iran be different today if Sen. John McCain had been elected president last November?

Of course it’s all speculation, but I’m guessing his policy wouldn’t be all that different except in tone from the policies being pieced together by President Barack Obama.

Obama continues to  hope for diplomatic openings to Tehran, but that effort hasn’t gone very far, in large measure because the leaders there don’t seem much interested in talking.

Republicans are critical of Obama for not being more vocal in supporting Iranian dissidents after the disputed reelection of President Mahmoud Ahmadinejad last month, and McCain has been at the head of the pack.

“He should speak out that this is a corrupt, flawed sham of an election, and that the Iranian people have been deprived of their rights,” he said on NBC’s Today Show recently. “We support them in their struggle against a repressive, oppressive regime and they should not be subjected to four more years of Ahmadinejad and the radical Muslim clerics.”

But I’m guessing that if he was in the Oval Office instead of the Senate, McCain would have heard – and listened to – the same advice as President Barack Obama: be very careful about making strong statements that would almost certainly be  regarded as meddling, something likely to narrow the yawning gap between the Iranian people and their nasty government.

Sanctions? Probably no difference here. Congress is moving slowly toward toughened sanctions, but there are still huge holes in the sanctions process, thanks to countries like Russia and China. All the tough talk of the Bush administration did nothing to plug those holes, and I can’t see how a tough-talking McCain would have had very different results.

What about the military option?  There’s little doubt Obama is less inclined to use and threaten military force in the region.  But McCain would have been restrained by Pentagon officials concerned about a military exhausted and depleted by two long wars and by the tactical problems of hitting and seriously disrupting Iran’s nuclear program.

McCain would have been bolder in brandishing the military option, but the leaders in Tehran are pragmatists who have a pretty good understanding of the limits of U.S. power in this crisis and the likelihood any president would be constrained by a war-weary public.

So while the tone of a McCain administration would probably have been very different, the net result on Iran would probably have been similar to the results under Obama: continued U.S. concern, continued confusion over how best to stop Iran’s nuclear program and continued consternation in Israel about the lack of good options.