Well, yeah; otherwise, it’d be awfully hard to explain what happened to Grover Cleveland.
I just wonder if the fact that we see much more of the elected candidate leads us to believe that he is more charismatic. If Dukakis had beaten Bush, we may have gotten to know him better, therefore tainting our perception of his charisma.
What you would really need to test this would be documentation of widespread opinion of the candidates’ respective charisma prior to each election. Right now, I think, both sides would agree that Obama is the more charismatic candidate (that’s why the Republicans are emphasizing his “celebrity” status, because they can’t deny it), so this November should be a test.
Right now Romney’s thinking, "Damn, if only it were Gore! I could out-charisma him!"