CNN is missing something interesting in its exit polls tonight.
According to the numbers they showed earlier, about half of the voters in the Alabama and Mississippi GOP primaries said that Romney was the most electable candidate. Of them, roughly two-thirds actually voted for him. Two-thirds of one-half = one-third of the whole.
Now look at the votes coming in. Romney's getting roughly one-third of the total in both states. That means that the only people voting for him are those who think he can beat Obama. Nobody is voting for him if they don't think he can win the general election.
Santorum and Gingrich are both pulling in votes for other reasons. People might not think they're the best candidate to beat Obama, but they get behind their guy anyway.
Romney? Basically nobody is voting for him for any kind of ideological reason. They are only voting for him if they think he can beat Oboogeyman.
Ask the Democrats in 2004 how well it works out when you nominate a candidate purely because you think he's your best shot at beating the other guy, and not because you actually like him or anything.