Florida, of course. Rubio losing would make the evening a terrible one for me, regardless of who becomes president. I think I may have to give up on all my hopes regarding America's political future if that happens (and it's likely to happen).
How so?
I think Hillary will end up winning Florida by a reasonable margin and given Rubio's low approval rating it doesn't seem too likely he will run ahead of Trump enough to win. Also, Murphy is a strong candidate. I don't think Rubio is going to survive this.