Things have gotten so bad for Mitt Romney that abruptly releasing his tax returns must seem like a welcome respite.

Battered by criticism of his “47 percent” video, dropping in the polls and battling a general sense that the election is slipping away, the Republican nominee is choosing to return to an issue on which Democrats have been hammering him for months.

That’s right, talking about his tens of millions of dollars in investment income, and a lower tax rate than some workers pay, now constitutes a positive development for Romney—because it enables him to change the subject.

On the surface, there was nothing terribly damaging in the documents released Friday. They show that Romney earned $13.7 million last year and paid 14.1 percent of that in taxes, slightly higher than the 13.9 percent he paid in 2010.

The campaign also said that the couple averaged an effective annual federal tax rate of 20.2 percent between 1990 and 2009, and never paid an effective rate below 13.6 percent. So much for the speculation, by Harry Reid and others, that Romney paid zero in some years.

Which raises the obvious question: why on earth didn’t Romney do this sooner? Why didn’t he put the questions and criticism to rest by releasing more returns, or at least the numbers? Has a small army of accountants been poring over the returns since the primaries? (Romney’s financial trustee told my colleague Daniel Gross that, among other things, the accountants had to wait until all the partnerships Romney owns reported their financial data.)

Perhaps Romney’s release takes the question off the table in the upcoming debates, rather than hanging over his head like a black cloud.

The downside of Romney’s move is that it brings the tax issue back to the fore. The Obama campaign can point out that by releasing a second year of returns, as Romney had previously promised to do, he is still far short of the standard set by his father, George Romney, during his 1968 presidential run.

But if the chattering classes weren’t chattering about Romney’s taxes, they’d be yapping about his surreptitious video embarrassment, his quick-trigger response to the attack on Libya, his campaign’s internal backbiting, or how he’s fallen behind in most key swing states. Instead, they can talk about how Romney is indeed rich—no news flash there—but did fork over nearly $2 million last year to Uncle Sam. Not that the 47 percent are going to feel sorry for him.