Voters have a tendency to go for the more manly candidate. Look at the post-ww II history. Ike, famous army general, JFK, war hero and movie star handsome, LBJ long, tall Texan running against jewish guy, Nixon running against Humphrey who was an older wimpy liberal, Carter was a former sub commander, running against ex-football jock Jerry Ford who had Watergate baggage, Reagan, movie star/cowboy/lifeguard man's man, Bush 41, war hero pilot, Clinton handsome rogue who ran against two elderly guys, Bush 43, fighter pilot/cowboy.
Now John McCain, a walking profile in courage, Navy fighter jock who served five years of hard time, against a wimpy grown-up Erkle? The pattern does seem to break down when a young vigorous although wimpy candidate faces a more macho but significantly older candidate. That would be the Clinton elections and the Carter election. So there may be hope for Obama, but he has to find a way to play the age card, a dangerous move with an increasingly aging population. McCain's age was not a problem at all for him in Florida, in fact it helped him.