Sarah Palin was, by far, a bigger draw than John McCain. But you just can't have that destructive dynamic when you are trying to win the presidency. It's a no-no in politics. In Hollywood, they call it "upstaging."
Marco Rubio is a rising Republican superstar. He'll get his own shot at the White House. He doesn't need to risk his political future by possibly being on a losing ticket this year. And he doesn't need to waste four years of his life as VP if Obama is dethroned.
And anyway, where do you think Marco Rubio would do the most good during the next four years? Attending funerals for the ex-presidents of Paraguay or Ukraine, or helping a Republican Senate vote down Obamacare?
I choose voting down Obamacare.