I guess you are assuming that one of these candidates will have a majority of the delegates making him the nominee going into the convention. Suppose no candidate has a majority and it results in open convention?I don't think so. I watched the clips of Marco Rubio at previous debate and he was a disaster. I also think his inexperience is against him and just all round he's a weak candidate, who unfortunately comes across like a classic puppet.
You're right. Rubio is definitely an overall weak candidate. I wonder if he wouldn't have been smarter if he'd hung back and tried to position himself from the outset as the prime VP pick. Rubio would do much better for himself to take the VP roll to a strong candidate, eventually growing into a Presidential candidate that the people just couldn't resist.