Mitt Romney has had a bad weak. His refusal to release his tax returns, a precedent for presidential candidates going back decades, has put the campaign on defense for several weeks now. Despite attempts to push the conversation elsewhere by calling President Obama a liar and having surrogates claim that the president needs to “learn how to be an American“, the Romney campaign is still in a defensive fetal position.

What would be the best way to change the subject? Announce a running mate. By picking a running mate this week the Romney campaign could distract the media’s attention away from his liabilities (the tax returns, his “retroactive” retirement from Bain Capital, etc.) and towards a flashy new subject. Of course this is just pure speculation, but if I were advising the Romney campaign, it would make sense to drop the bombshell this week.

Which leads us to the question: “Who?”

I’m going out on a limb and saying that Romney will pick Paul Ryan. There are three main reasons: Romney has already said that he supports the controversial Ryan budget which ends Medicare and turns it into a voucher program so it will be used as a weapon against him anyway. Ryan can also bridge the Tea Party, where Romney has a clear weakness, with the more mainstream business-oriented wing of the party. The third reason is that the Romney people really think that they have a shot in Wisconsin.

The polling does not bear this out, including exit polls from the Wisconsin recall, but the success of Scott Walker in June might tempt them to roll the dice. Wisconsin is the closest thing to a swing state from any of the potential veeps outside of Rob Portman’s Ohio. Tim Pawlenty comes from decidedly blue Minnesota and John Thune from deep red South Dakota. Of course Dick Cheney came from the reddest of red states in Wyoming and that didn’t stop George W. Bush, but then again, the Bush campaign needed someone with foreign policy credentials on the ticket. To that extent Romney needs some credibility with the Tea Party. Ryan would give them that without compromising the ticket (too much).