Think about it. Through a week of a Democratic convention, when his tax returns will be mentioned by speaker after speaker. Through the early fall campaigning. Through the debates, when he will again say that he feels he’s revealed all he needs to reveal. Through the campaign’s final, home-stretch weeks. If he hasn’t released more returns, then by mid-October, this will be one of three main things the average American knows about Mitt Romney: that he’s rich, that he’s running for president, and that he won’t release his tax returns.

That will have to be devastating. And it will be something he brought completely on himself, either by refusing to release the returns or by doing whatever it is he did in the first place that he’s now hiding. My Beast colleague Peter Beinart is correct to write that how much Romney paid in taxes doesn’t have anything to do with the larger debate we’re having in this election about “whether the federal government should try to significantly regulate capitalism.” But it has everything to do with Romney’s character—his sense of entitlement, the Master-of-the-Universe-y aura of impatient superiority that was undoubtedly a great virtue in the corporate world but is very much the opposite in the civic one, and the weird insecurity that lurks underneath that veneer of über-confidence. And those things are very germane to what sort of president he’d be.