Opposing party: Who's nomination do you fear the most?

[Averroës Nix]

The perennial-overrated Senator from Florida terrifies me, but I think he's a lot less electable than most people realize.

Obviously, I've never liked Cuomo, but he's already disliked among the Democratic base and he would be a lightning rod if he ran.

I see a lot of people mentioning Santorum as a candidate whom they fear "ideologically." I disagree; just scanning Wikipedia for potential candidates, I see several (potentially) serious candidates who could be far worse - Brownback, Ryan, and Walker being foremost among them.