Ben Smith at the Politico notes the high rate of Republican voters in Mississippi's primary, who overwhelmingly supported Hillary Clinton. Are they genuine Clinton supporters, or just GOP partisans trying to prolong the Democratic primary or help the weaker candidate? One suggestion for the latter possibility is that Rush Limbaugh urged his listeners to vote Clinton before the Texas primary.
Smith says he's skeptical, because "Rush wasn't campaigning for Hillary in Mississippi." Hmm. Limbaugh's program does cross over state lines, and Mississippi Republicans surely understand that what's good for one primary is probably good for another. So the absence of Limbaugh explicitly telling his audience to vote for Clinton in Mississippi doesn't seem to be very important.
Meanwhile, Daily Kos diarist georgia10 notices an interesting thing from the exit polls: a full 15% of Clinton voters in Mississippi said they would be dissatisfied if Clinton is the nominee. Now, it's hard to figure out what that really means. A much smaller figure, 4%, of Obama voters said they'd be dissastisfied if Obama is the nominee. So why are all these Clinton voters saying they'd be unhappy if the candidate they voted for wins? It's impossible to know for sure. Maybe they wished they could have a choice other than Clinton or Obama. Maybe they want a candidate who's not only white but also male (which would explain why the "dissastisfied with their own preference" vote went so heavily to Clinton over Obama.)
But I think the mischief-making crossover vote is the best available explanation here. I don't recall much genuine fondness for Hillary Clinton among Republicans in the Deep South.
Update: The Jed Report has stronger evidence.