A new Washington Post poll shows, amazingly, that President Obama’s release of his “long form” birth certificate actually did have a big impact on the Birther delusion: Poll: Number of ‘birthers’ plummets.

In interviews following the public release the president’s “long-form” birth certificate last week, fully 70 percent of Americans say Obama was born in Hawaii, a big bump-up from the 48 percent who said so a year ago. Even more say he was U.S.-born, or call that their best guess, for a total of 86 percent.

Overall, 10 percent of Americans say Obama was likely born abroad, down from 20 percent in an April 2010 Post-ABC poll. Almost all those who now say Obama was born in a foreign country say that it’s only their “suspicion;” just 1 percent claim “solid evidence” that the president was born elsewhere (9 percent said so last year).