WHO or WHO? I would expect any presidential candidate to announce, after nomination, a nationally known figure who would seem to be likely to complement the Pres. candidate's talents, as well as help attract voters from a strategic area.
If Romney is the eventual nominee, he's going to need someone from the south, midwest or southwest in order to balance the ticket. Both attract a kew demographic (midwesterners for Pawlenty, actual conservatives for Romney).
As far as a "nationally known figure", how much name recognition do you think Dick Cheney had?