From ABC News:
“So, if Mitt Romney asks, you will you say no?” [National Journal's Major] Garrett asked.
“Yes. But you know he’s not going to ask. That doesn’t work. He’s watching this interview right now,” Rubio, 40, said.
Rubio even went as far as recommending another U.S. senator for Romney to consider in his VP vetting: Ohio Sen. Rob Portman.
“The bigger point is we’ve got a lot of really talented people out there that Mitt Romney can get to pick from,” Rubio said. “And I think a lot, Senator Rob Portman would be a phenomenal choice for vice president. That’s where I would encourage him to look because I’m enjoying my service in the Senate.”
However, don’t expect the Rubio veep speculation will be slowed even a smidgen by this definite answer: Rubio slipped up at one point in the event, and said, “If in four to five years, if I do a good job as vice president—I’m sorry, as senator—I’ll have the chance to do all sorts of things.”