WASHINGTON — It’s not just the death of Osama bin Laden that’s causing a swing in the polls.

New data released by the Washington Post shows that President Barack Obama’s decision last week to release his long-form birth certificate may have successfully erased doubts among many about whether he was born in the United States.

In a survey conducted after Obama decried the “sideshow” of conspiracy theories about his birthplace, 10 percent of respondents still said the president was born outside of the country, a drop from 20 percent in a similar poll conducted one year earlier.

Of that 10 percent, just 1 percent said there is solid evidence that he was born in another country, while 8 percent said their answer was based purely on suspicion.

The drop was across partisan lines, but most pronounced among Republican respondents. Nearly a third, 31 percent, in last year’s poll said he was born in another country, something that would make him constitutionally ineligible for the office of president. But now, 14 percent of Republicans said they held that view, a drop of 17 percentage points.

Last year, just 48 percent of respondents correctly identified Hawaii as the place where Obama was born; this year, 70 percent responded that way.

Obama started his speech at the White House correspondents dinner on Saturday by joking once again about the controversy, with a montage set to the tune of “Real American.”