Start to read Seth Mandel‘s Commentary blog entry on political “evolution,” and you’re likely to expect the following takeaway: President Obama deserves at least as much attention as Republican rival  Mitt Romney for political flip-flops. But Mandel actually offers a more interesting analysis.

He highlights a study that suggests the degree to which someone cares about flip-flopping depends on the degree to which he favors the political philosophy associated with John Stuart Mill or the one linked to Edmund Burke. Left-of-center thinkers tend to side with Mill, while those on the right tend to support Burke’s approach.

That conservatives were more drawn to a Burkean philosophy on governing isn’t too surprising. Far more interesting is the finding that liberals are much less likely to object to flip-flopping in the first place.

This helps explain why someone like John Kerry–a starkly unlikable figure for whom the label “flip-flopper” seemed particularly apt–could win the Democratic nomination despite all the obvious red flags of his candidacy. It also helps explain why Mitt Romney had such difficulty winning the Republican nomination even though he had a four-year head start and aside from Rick Perry, who possessed a strong record but who stumbled badly in the debates, the path seemed clear for Romney. He struggled not against other strong candidacies but the popular composite candidate known as Not Romney.

It is conservatives, therefore, who branded Romney a flip-flopper long before he had the chance to face John Kerry’s fate of being so labeled during the general election. The right, not nearly so tolerant of unprincipled politicians as the left, immediately flagged what seemed like Romney’s politics of convenience.

The other key takeaway from this is that it surely depends on which issues a candidate flip-flops.