Even Republicans are now begging Mitt Romney to put out his tax returns and "take the hit for a day or two." And Romney is flat-out refusing. That's what the new Obama ad that Dominic posted this morning is all about. Here's some of the text of that ad:

Romney admits that over the last two years he’s paid less than 15 percent in taxes on $43 million in income. Makes you wonder if some years he paid any taxes at all. We don’t know because Romney has released just one full year of his tax returns. And won’t release anything before 2010...What is Mitt Romney hiding?

This isn't a deliciously brilliant ad like the one that appeared over the weekend, but it's a solid attack ad. And as a graduate of Glenn Beck University, I have to note that this Obama ad steals a page from Glenn's I'm-just-asking-questions-here school of inquiry. That's a smart move in this case.

I can't imagine that the Romney campaign hasn't run the public-relations calculations on these tax returns. And if they've run the calculations and they're stonewalling on releasing the returns, that means that whatever is in these returns is a campaign-ending issue. So now they're betting that the imagination of the American public isn't as terrible as the truth of what's in these returns. That's a risky bet.