Ben Domenech has been doing some pretty solid reporting in The Transom (you’ve subscribed, haven’t you?) about what might be in Mitt Romney’s taxes. He offers this morning the best and most informed theory.Why most informed? Well, he talked to people who were familiar with the veep vetting process for McCain in 2008.Here’s what he reports:

So what about the years before 2009? We know he turned over more than two decades of returns to the McCain campaign during the veepstakes vetting process. What was in them? “Mitt’s taxes were complex, but clean. He overpaid his taxes. An honest appraisal would find nothing to criticize, though Romney’s staff, for better or worse, doesn’t seem to trust the returns to be honestly appraised by the media,” says a source closely familiar with the 2008 vetting process. “To be clear, there’s stuff in the tax returns the dishonest or ignorant can snark at, though it pretty much comes down to criticizing Romney for being rich. There’s nothing indefensible, but as with a lot of the attacks on Bain, Romney isn’t defending. As a game theory matter, people are going to assume the worst. But presidential general election politics seems to be about something other than dealing directly and straightforwardly with issues, so maybe this strategy is focus-grouping better with disengaged independents.”