So it will not quiet the most avid attackers. Several quickly questioned its authenticity. That’s because the birther question was never really about citizenship; it was simply a proxy for those who never accepted the president’s legitimacy, for a toxic mix of reasons involving ideology, deep political anger and, most insidious of all, race. It was originally promulgated by fringe figures of the radical right, but mainstream Republican leaders allowed it to simmer to satisfy those who are inflamed by Mr. Obama’s presence in the White House.

Sarah Palin said the birth certificate issue was “fair game,” and the public was “rightfully” making it an issue. The House speaker, John Boehner, grudgingly said in February that he would take Mr. Obama “at his word” that he was a citizen, a suggestion that the proof was insufficient. He said, however, that it was not his job to end the nonsensical attacks. “The American people have the right to think what they want to think,” he said at the time. That signal was clearly received. Lawmakers in nearly a dozen states introduced bills requiring presidential candidates to release their full birth certificates.

It is inconceivable that this campaign to portray Mr. Obama as the insidious “other” would have been conducted against a white president.

There was a price to the party for keeping the issue alive; inevitably, it was picked up by a cartoon candidate, Donald Trump, who rode birtherism directly to the prime-time promontories of cable TV. The Republican establishment began to wince as it became increasingly tied to Mr. Trump’s flirtations with racial provocation, and Karl Rove told him to knock it off. Naturally, he did not.

Finally, his taunting and the questions of television correspondents obliging Mr. Trump got on the president’s nerves. Mr. Obama was tactically smart to release the certificate and marginalize those who continue to keep the matter alive. It is tragic that American politics is fueled by such poisonous fire. Mr. Trump quickly moved on to a new fixation, questioning Mr. Obama’s academic credentials. Mr. Boehner, and other party leaders, have a new reason to call a halt to the politics of paranoia and intolerance.