Charming candidates win elections: George W. Bush, whatever his other flaws, could be very charming; John Kerry, not so much. Hillary Clinton might have beat Barack Obama in the 2008 primary, if only her smile was as endearing as his.This, as regular readers of this blog know, gets it entirely backwards. Winning causes candidates to "acquire" charisma; losing causes politicians to lose it -- or, as Brendan Nyhan put it a ways back, "the political climate creates charisma." Clinton's smile would have been (thought to be) more endearing than Obama's had she won; Kerry would have been (thought to be) the charmer, while Bush's locker-room style would have been (thought to be) an arrogant smirk.
The easiest way to see this, of course, is to compare press impressions of the personalities of presidents as they go from popular to unpopular over time (i.e. LBJ 1964 vs. 1968, RMN 1972 vs. 1974, JEC 1976 vs. 1980, GHWB from 1988 to 1992 -- yes, all four of those had charisma for a while, at least per the press). Or, for losing nominees, from spring to fall -- Kerry wasn't charmless in spring 2004, and McCain had plenty of charisma around the time he knocked Romney out in spring 2008.
Don't worry: if Mitt Romney wins the nomination, he'll turn out to have had plenty of charisma; if he wins in November 2012, he'll have charisma to spare. At least until (or unless) things start going badly.