Trump is in it to win it, he's made that clear. But as soon as he sees it going south and sees that he has no chance of winning, he'll jump ship.
Paul would be a decent pick (and he's a zad

lol) but there's NO WAY he could make up for lost time and get people on his side within 3 months. Not unless republicans plan on voting for him just to vote for him without hearing his full thoughts on policies, etc and even then I still don't know if he'd win.
Let's hope Trump sticks it out and continues to be messy inadvertently handing our good sis Hillary an easy win.