When will Santorum drop out?

[Ⓐnarchy in the ☭☭☭P!]

Depends. If he somehow was beaten by Paul in Florida (which, frankly, is about a million in one chance) he'd almost certainly drop out immediately in outrage and endorse Newt or Romney. Seeing as how that's effectively impossible, I'd peg it to occur some time after Super Tuesday, where he'll more likely than not flounder with Newt taking his support away (if he doesn't, it's almost certainly indicative of a Romney comeback and win).