Various Republican presidential wannabees are assailing Barack Obama on the Libya issue – wow, who could have ever predicted such a thing? – and of course they would be banging the drum regardless of what he had chosen to do. Obama’s choice is hardly perfect, as I noted earlier this week, but we all know the partisan drill: If Obama had stormed into Libya three weeks ago, with or without United Nations cover, the GOP aspirants would be complaining (a) that his hasty action was symptomatic of his naive inexperience, and (b) that he was imperiling our servicemen and servicewomen by rashly broadening their global mission, thus potentially weakening America.In other words, much of what we’ve heard thus far from the ’12 Republican camp is fairly worthless. Tim Pawlenty and Sarah Palin, undoubtedly drawing on their estimable foreign policy experience, contend that Obama took too long to intervene. Meanwhile, Newt Gingrich complains that “it is impossible to make sense of the standard for intervention in Libya except opportunism and news media publicity,” and I frankly have no idea what he’s talking about, since Obama would have reaped “news media publicity” for whatever decision he ultimately made. It’s a weird complaint anyway, given the fact that Gingrich himself is such a veteran master of opportunism, this being a classic example: Back on March 8, Gingrich told Fox News that we should intervene with a no-fly zone; but this morning, in the wake of Obama’s intervention, Gingrich told The Today Show, “I would not have intervened.”Another noteworthy armchair general is Rudy Giuliani. He’s probably not running for president – not after his ’08 performance, when he spent $60 million and won only one delegate, thus setting a new record for nomination failure – but he keeps showing up in primary hotbeds such as New Hampshire. Hence his inclusion here. He hammered Obama’s Libya move the other day, calling it “the most perplexing decision-making I’ve ever seen by an American president” (really? the most perplexing decision-making ever?), and he chalked it up to Obama’s “lack of experience.” As if Giuliani has any foreign policy experience. He had a chance to get some back in 2006, when he was named to the bipartisan Iraq Study Group – but he quit to make speeches at $200 grand a pop; during a key month when ISG members were digging in to the fine points of Iraq policy, Giuliani was on the road pocketing more than $1 million.Anyway, everything above is mere foreplay. We now arrive at the main event, Mitt Romney. We’ve long known, of course, that Romney makes a weathervane look like a concrete pylon. But bear with me for the latest manifestation of this truism.Surfacing Monday on the conservative Hugh Hewitt radio show, Romney said: “Thus far, the President has been unable to construct a foreign policy, any foreign policy. I think it’s fair to ask, you know, what is it that explains the absence of any discernable foreign policy from the president of the United States? And I believe that it flows from his fundamental disbelief in American exceptionalism. In the President’s world, all nations have common interests, the lines between good and evil are blurred, America’s history merits apology. And without a compass to guide him in our increasingly turbulent world, he’s tentative, indecisive, timid and nuanced.”This stuff is aimed, of course, at the Obama-hating caucus-goers in Iowa and their primary season counterparts in South Carolina, so here’s what Romney is really telling his audience: “I will morph myself into whoever you want. I will say or do anything to get your votes. I will wash all your cars. Would Turtle Wax be OK?”So I won’t spend much time assessing the substance of what Romney said, except to point out that one key line – about how Obama’s failure in Libya supposedly “flows from his fundamental disbelief in American exceptionalism” – is nonsensical. Because Obama’s stated purpose for going into Libya, to protect civilians from slaughter, is precisely about American exceptionalism. By ordering an humanitarian intervention, Obama is signaling that America indeed considers itself a moral force for good in the world.And another Romnney complaint – “We’re following the French into Libya” – was flat wrong. I understand the need to feed red meat to the voters who will make or break his second presidential bid – French equals effete equals nuanced – but by the time Romney uttered that line on Monday, France’s role had long been supplanted by the launching of more than 100 American cruise missiles, and the whole operation was essentially being run by the Americans.But now comes the weathervane moment. Back in 2007, when Romney visited the Sean Hannity show, he was asked to comment about the various Democratic attacks on George W. Bush’s handling of the Iraq war. Romney replied that such criticism “is one of the things that’s most frustrating to me. I go back to something that Senator Vandenberg of Michigan said a long time ago – politics ends at the water’s edge. It’s supposed to.”Really? Arthur Vandenberg’s late-’40s credo is Romney’s preferred standard? Then why is ’11 Romney attacking the commander-in-chief beyond the water’s edge, thus behaving in a way that would be “most frustrating” to ’07 Romney? Easy answer: Because the winds have shifted, and the standard now (to borrow Gingrich’s word) is opportunism.The classiest Republican aspirant, by the way, is Haley Barbour. Over the weekend, he said simply this: “Whenever our men and women are involved in military action, every American stands with them and supports them as I do. This is not the time to critique what the administration has done or will do.”That should cost him votes in the early Republican primaries.