Santorum has always sounded like a politician, as far as I’m concerned.
A Romney nominee picking a Santorum for vp would make the Romney ticket look worse, not better.
A candidate like Romney would have to pick someone with qualities opposite his own—Santorum is too similar to Romney.
I bet Romney picks Rubio if he wins...or someone like that. And despite what Rubios is saying now, if it comes down to it, and it is needed for the country and to defeat Obama, IMHO, he’ll take the job.