Here's a random thought from the South Carolina CNN exit poll: 4% of people who said that Obama is the most qualified to be Commander-in-Chief voted for Clinton.
Pretty well the only complaint I've heard leveled against Obama in favor of Clinton is that he isn't qualified to be Commander-in-Chief. So what person would respond that he's the most qualified and then vote for Clinton?
I'm honestly wondering; this isn't meant as a snarky jab.
Perhaps something like women who want a woman president and feel that Clinton would still do a good job even if Obama would do a better one - just a possibility. Also there may be people who think Obama just couldn't win the general while Clinton could.