However, birther beliefs continue to persist among 21 percent of the public. Most notably, 33 percent of Republicans still say Mr. Obama was not born in this country, though this figure represents a significant decrease from January, when 51 percent of Republicans endorsed the myth. (Twenty-two percent of independents and 10 percent of Democrats still endorse it as well.)

The Morning Consult estimates confirm the findings of a Huffington Post/YouGov poll conducted after Mr. Trump’s announcement. That poll also found that more people now think Mr. Obama was born in the United States, though approximately one in five continued to say they thought he was ineligible for the presidency.

These results highlight both the potential and the limits of corrective information. Mr. Trump’s statement renouncing the myth might provide an especially credible and persuasive signal about the falsity of the claim to true believers.

Yet the human capacity to resist contradictory evidence can be remarkable. According to a report in Politico from a recent Trump rally, for instance, “the birthers and non-birthers all seemed to think that Trump has privately agreed with them all along, and all praised his flip-flop as a shrewd political stratagem to change an inconvenient subject.” Mr. Trump himself said Wednesday that he reversed himself because “we want to get on with the campaign.”