Paul Krugman approves of the Obama campaign’s decision to continue hammering Mitt Romney on his history with Bain Capital and his refusal to release any tax returns prior to 2010. He says,

“…this election is, in substantive terms, about the rich versus the rest, and it would be doing voters a disservice to pretend otherwise.

“[...] The print media do offer analysis pieces — but these pieces, out of a desire to seem “balanced,” all too often simply repeat the he-said-she-said of political speeches. Trust me: you will see very few news analyses saying that Mr. Romney proposes huge tax cuts for the rich, with no plausible offset other than big benefit cuts for everyone else — even though this is the simple truth. Instead, you will see pieces reporting that “Democrats say” that this is what Mr. Romney proposes, matched with dueling quotes from Republican sources.

“So how can the Obama campaign cut through this political and media fog? By talking about Mr. Romney’s personal history, and the way that history resonates with the realities of his pro-rich, anti-middle-class policy proposals.

“Thus the entirely true charge that Mr. Romney wants to slash historically low tax rates on the rich even further dovetails perfectly with his own record of extraordinary tax avoidance — so extraordinary that he’s evidently afraid to let voters see his tax returns from before 2010. The equally true charge that he’s pushing policies that would benefit the rich at the expense of ordinary working Americans meshes with Bain’s record of earning big profits even when workers suffered — a record so stark that Mr. Romney is attempting to distance himself from part of it by insisting that he had nothing to do with Bain’s operations after 1999, even though the company continued to list him as C.E.O. and sole owner until 2002. And so on.

“The point is that talking about Mr. Romney’s personal history isn’t a diversion from substantive policy discussion. On the contrary, in a political and media environment strongly biased against substance, talking about Bain and offshore accounts is the only way to bring the real policy issues into focus. And we should applaud, not condemn, the Obama campaign for standing up to the tut-tutters.”