Mitt Romney’s campaign is taking heat for declining to disclose more than the two most recent years’ worth of his tax information. Even conservative commentators such as The Washington Post’s George Will and the Weekly Standard’s Bill Kristol are saying it’s past time to come clean. Of course, members of Romney’s team, unlike their friends on the outside, presumably know what the documents would reveal, so we should probably assume that they have fairly good reason not to release them. Could the criticism Romney would suffer over the contents of the returns be worse than the criticism he’s getting for not disclosing them? Here are some guesses about legal — but potentially embarrassing — things in Romney’s tax returns:

Profits from the financial crash

The vast majority of American families lost wealth in the housing bust of 2007-09 and the financial crisis that came in the middle of it, and millions lost jobs or earnings. But it was possible for a canny or lucky investor to profit from the chaos — especially for a wealthy individual with access to unusual financial products. Maybe Romney made a lot of money through bets on skyrocketing foreclosures or well-timed investments in bailed-out banks. There’s nothing wrong with smart financial planning, but making money on the crash could be awkward for a politician. There’s a tension between promising to make things better and profiting off human misfortune.

A low tax bill because of the crash

There’s also the possibility that Romney’s investments lost some value during the crash years and that he combined this with aggressive exploitation of loopholes to pay a strikingly low tax bill. One rumor was that he managed to pay nothing in taxes, something his campaign has denied. But would paying $2.75 really look all that different from paying $0? A super-low tax bill would turn Romney into the poster child for President Obama’s very popular “Buffett rule” proposal, which aims for a minimum tax level on high-income individuals.

Swiss bank amnesty

We know from the tax documents Romney has released that he once had a Swiss bank account, a fact that the Obama campaign has played up in ads. But his 2010 tax return did not include a Report on Foreign Bank and Financial Accounts form (“FBAR” to accountants) detailing his offshore investments. In 2009, the Swiss government began to relent on its traditional banking secrecy rules, and banks turned over information about tens of thousands of American tax scofflaws to the U.S. government. To help deal with the crush, the IRS staged a limited-time amnesty in 2009 for American citizens with previously non-disclosed foreign accounts to pay their back taxes without penalty. It’s possible that earlier tax documents or the 2010 FBAR would show that Romney took advantage of the amnesty. While legal, this would amount to a problematic confession of past wrongdoing.

None of the above

The possibilities are endless. Romney’s vast wealth has already provided plenty of campaign fodder — from his car elevator to his proposed $10,000 bet with Texas Gov. Rick Perry during a debate — so almost any additional details about his finances would add fuel to the fire. But the most likely candidates for compromising revelations could relate to the 2008-09 period. Romney isn’t disclosing his 2006 or 2007 taxes, but by his own two-year standard he would have had to if he had won the 2008 Republican nomination. That makes the time between his presidential runs — a period that coincides with major upheavals in financial markets and bank secrecy practices — far and away the most likely window for something more politically worrisome than a reputation for reticence.

Matthew Yglesias , Slate’s business and economics correspondent, is the author of “The Rent Is Too Damn High.”

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