Clinton, authentic
if you're Bill Clinton, you have to look at it this way: for your entire career as a candidate, other politicians tried to paint you as waffling and slippery, and not once did it actually work. (Well, there was that gubernatorial defeat in 1980, but that had more to do with Jimmy Carter and a bunch of Cuban refugees than anything else.)
Meanwhile, you won a couple of national elections by positioning yourself as the pragmatic bulwark against conservative extremism on one side and liberal excess on the other. So it would be natural to have learned that it makes more sense to exploit your opponent's rigid ideology than his general squishiness.
But Mr. Clinton's situation was different from either Mr. Romney's or Mr. Obama's. For one thing, Mr. Clinton's brand of centrism -- which Republicans, and a lot of Democrats, tried to portray as expedient -- actually sprang from a coherent worldview. The charges of inauthenticity never seriously wounded Mr. Clinton because, unlike Mr. Romney, he had been remarkably consistent throughout his political life, and where there was inconsistency, Mr. Clinton had a singular ability to argue his way out of it.