The theory does accord with the last several general elections, but it doesn't seem to accord with primaries. For example, Herman Cain, Howard Dean, and Mike Huckabee all lost out to less charismatic candidates. Since primaries are now decided on a similar basis to general elections--debate performance, fundraising, retail politics--it seems like these data points ought to be included.

I suspect taking office makes a candidate seem more charismatic in retrospect, an example of a choice-supportive bias:

http://en.wikipedia.org/wiki/Choice-supportive_bias

If true worth noting that while this may not be unique to the US, it's certainly not universal.

Hollande beating Sarckozy in France recently would be a pretty solid counter example, similarly John Major winning in the UK in 1992 (Kinnock was no Kennedy but next to Major anyone looks charismatic).

"Of course your president is an actor, he's got to look good on TV!"

-Emmett "Doc" Brown

Thanks, I hadn't seen this. Certainly the case in the last 4 or 5 elections. It's why Obama killed Romney with young voters.

That awkward kiss between Al and Tipper also comes to mind.