Andrew comments  on Romney’s political weaknesses:
If Romney cannot win a Southern state with Christianist voters or keeps losing the white working and lower middle class, he’s a very weak nominee. Which means he will have to pick a red-blooded red-stater as a veep. I think Rubio’s Mormon period effectively rules him out as an option. My suggestion? Huckabee as veep. He balances every Romney weakness.
Huckabee would make an interesting choice. It would mean that Romney was tying himself to the person who once said  that he had no soul. The Democratic ads would practically write themselves: “Even Mitt Romney’s running mate has said that he has no integrity and will say anything to win an election.” It would likely horrify the economic conservatives who found Huckabee so unacceptable last time, and it would also saddle the ticket with Huckabee’s ethical baggage that the media never bothered digging into last time.
As for Rubio, there are many reasons  why it would be a mistake to select him as Romney’s running mate, but the story about Rubio’s childhood Mormonism isn’t one of them. Anyone who is going to have a problem with the ticket because Rubio was briefly a Mormon long ago as a child will already be opposed to supporting Romney anyway, and Christian conservative voters typically don’t punish a politician if he is currently a practicing Christian. This is why Christian conservatives have had no problem supporting Jindal and Haley. Romney could choose Rubio, but the most important reasons why he shouldn’t are clear: Rubio’s experience at the national level is simply insufficient, and he is not yet otherwise qualified to be the next in line to the Presidency. Selecting Rubio would generate a lot of enthusiasm among movement conservatives, which addresses one of Romney’s problems, and it wouldn’t turn into a debacle the way Palin’s selection did, but it is still a bad idea.