I think Romney is doing so poor with Latinos, that he's going to have to choose Rubio or Martinez.
If he chooses Rubio, there's a significant chance it could blow up in his face. This is a guy who hasn't been vetted, has been somewhat flexible with the truth about personal aspects of his life (i.e. telling people his family fled Castro when they actually emigrated some time before he came to power), and has financial problems (underwater on his mortgage, tons of student loan debt) that could indicate some more skeletons in his closet.
Which Martinez? Mel or Susana? With regards to the first, this is not a good year to pick a lobbyist for a running mate. With regards to the second, she may end up being seen as a Latina Palin.