Wouldn't you have liked to have been a fly on the wall during that conversation?

CNN:

Marco Rubio, a senator whose name was floated first as a possible presidential, then vice presidential candidate, on Wednesday made an endorsement in the presidential race, saying, "It's evidently and increasingly clear that Mitt Romney is going to become the Republican nominee."

"We have to come together behind who I think has earned the nomination, and that's Mitt Romney," Rubio said of the former Massachusetts governor in an appearance on Fox News.

The primary process has been "very good," Rubio said, and the candidates "have a lot to be proud of."

"But I think we are at a stage where two of the candidates have openly admitted, the only way they can win a nomination is to have a floor fight in Tampa in August," Rubio said. "I don't think there is anything good about that. There is no way that a floor fight at the convention in Tampa in August is a recipe for a win in November. On the contrary, I think it's a recipe for disaster."

Rubio, a first term U.S. senator and tea party favorite who previously served a decade in the Florida state House, has repeatedly discouraged suggestions that he would join the GOP ticket. In the interview, he said he and Romney have talked, but "never about vice president, or anything like that." It is a suggestion he downplayed in an earlier interview.

Romney and Rubio may not have discussed the Veep spot directly, but you can bet their close advisors have done so. Rubio is wary of being used solely to attract Hispanic votes, while Romney wants to be assured that the much more conservative Rubio won't go off the reservation during the campaign. It's a delicate dance with Rubio needing some independence and Romney coveting Florida electoral votes, and perhaps a surge in Hispanic support that would help him in states like Colorado and Virginia.

Would Rubio demand a change in Romney's immigration policies as part of the package? A better question is how badly Romney needs Rubio (or some other Republican Hispanic) in the fall campaign? The answer is very badly. The two are not that far apart on immigration policy, and perhaps some way could be found to paper over the differences.

In the end, it comes down to this: Romney needs to get more than the 31% of the Hispanic vote that McCain received in 2008 if he is going to win in November. If Rubio can deliver another 10% of the Hispanic vote, his presence on the ticket will have been worth the trouble.