A few months ago, I ran an item reminding everyone that it's a complete waste of time to ask potential candidates whether they would serve as a running mate. The story is that there are lots of good reasons for people to say that they would not run for VP even if they would do so if asked...in fact, most people would accept the #2 slot if asked, in most circumstances, but lots of people would deny that before the fact. So there's really no reason to ask.
So, the follow-up: it's also a complete waste of time to ask a presidential candidate who he or she would choose as a running mater. And if any reporter does so, there's no reason to pay attention to the response. Example: Taegan Goddard reminds us today that Mitt Romney "seemed to rule out" Rick Santorum earlier, making Santorum's newly expressed interest in the job a moot point. Except all of it doesn't count: if Santorum says he's interested or not, and if Romney says he'd consider him or not. All of it should be regarded as posturing that has nothing to do with the actual VP selection. Not that there's anything wrong with it; there are some lies that I think are unethical when politicians tell them, but others -- including these sorts of career plan decisions -- are fine with me. And, as far as I can tell, fine with voters, too.