Steve Schmidt was recently quoted as saying that the reason Romney wasn't chosen was because he didn't want another wealthy man on the ticket.
This is why I believe Portman is unlikely...
I'm starting to think, if Ayotte is unlikely, than Jindal might be a frontrunner for the nomination. Susana Martinez remains the perfect pick if he can convince her to reconsider, of course.
I think Martinez's reasons for saying no are such that she'd get a lot of bad publicity if she now said yes.
My own hunch is that Romney will go for a safe, "do-no-harm," Boring White Dude type. It's how he's played the campaign so far.