Sure. As you say though, that would be a difficult sell.

I think part of the problem is that "they're changing their opinions too much" is usually a snap judgment. It tends to be applied to everyone that doesn't have a firmly fixed campaign platform (and isn't protected by party affiliation).

People who actually sit down and look over the available history tend to, just as a trend, come back with more concrete issues. More along the lines of "this guy's had a different opinion on foreign policy to go with every speech he's ever made, and it always lines up with the majority opinion of the audience."