“I’ve got better stuff to do,” President Obama declared near the end of this morning’s news conference, in which he unveiled a copy of his birth certificate, thus adding a redundant shovel of evidence to the mountain that already disproves conspiracy theories of his foreign birth.

But don’t you believe it. The president’s schedule is not loose. If he took precious time to address this absurd issue personally, it’s because he had nothing better to do, or at least nothing that he’d rather do. And the reason is obvious: Keeping the birther issue alive, while ostensibly laying it to rest, is hugely to his political advantage.

1. As he not-at-all-accidentally mentioned today, Obama is about to enter tense negotiations with the Republicans in the House and Senate over a debt-limit extension and deficit reduction. The polls show that the Republicans enjoy a slight but tentative edge in public opinion on this issue. The polls also show that a lot of the GOP base believes the birther stuff; there is a link, real and perceived, between the birthers and the Tea Party faction in the House. GOP establishment figures are desperately trying to distance themselves from the conspiracy theorists. But Obama has no interest in letting them succeed. The more he can cast himself as a reasonable guy who’s trying to deal with a bunch of nuts — people who, as he put it, “make stuff up and pretend facts aren’t facts” — the stronger his position on the budget will be.

2. At the moment, the potential contenders for the 2012 Republican presidential nomination include two men, Donald Trump and Mike Huckabee, associated with loopy views of Obama’s origins. Trump, especially, is a stunt candidate — I think he’s what Obama had in mind when he lashed out at “carnival barkers” today — whose prominence serves only to discredit the Republican Party generally.

By releasing the certificate in response to Trump’s demands, Obama builds him up in the eyes of some GOP rank and filers and makes it more likely that he’ll hang around to obscure the message of more serious candidates. Sure enough, no sooner had Obama appeared on TV than Trump followed with a news conference of his own, announcing that “I’m very proud of myself. . . . I feel I’ve accomplished something really, really important.”

3. As much as today’s presidential news conference exacerbated the GOP’s internal contradictions, it may also have helped shore up Obama’s own shaky Democratic base. If there’s anything loyal Dems believe, it is that their party is a last bastion of reason and fact beset on all sides by Palinite hordes. Blasting the birthers and, by implication, Trump, Obama reminds the faithful why they should come out strong for him in 2012, despite all the compromises he’s made since 2009.

“We do not have time for this kind of silliness,” The president said, then set off for Chicago to tape an interview with Oprah. Tonight, it’s on to New York for three — count ’em, three — political fundraisers.

I’d say he’s prepared the ground for those events beautifully.

UPDATE, 1:33 p.m.: Trump’s press conference actually came before Obama’s; the Donald spoke in response to the release of the birth certificate itself.