Washington ? It’s the conspiracy theory that won’t go away. And it’s forcing Republican officials and presidential contenders to pick sides: Do they think Barack Obama was born outside the United States and disqualified to be president?

As the Republican candidates tiptoe through the mine field, Democrats are watching. They hope the debate will fire up their liberal base and perhaps tie the eventual GOP nominee to fringe beliefs that swing voters will reject.

In recent days several prominent Republicans have distanced themselves, with varying degrees of emphasis, from the false claim that Obama was born in a foreign country. But with a new poll showing that two-thirds of adult Republicans either embrace the claim or are open to it, nearly all these GOP leaders are not calling for a broader effort to stamp out the allegations.

“It’s a real challenge for the Republican Party and virtually every Republican candidate for president,” contends Democratic pollster Geoff Garin. If it’s not handled well, he said, all-important independent voters might see Republicans as extreme or irrelevant.

Many Americans consider claims of Obama’s foreign birth to be preposterous, unworthy of serious debate. Yet the “birther” issue threatens to overshadow the early stages of the GOP effort to choose a presidential nominee for 2012. Real estate mogul Donald Trump has stirred the pot lately, repeatedly saying Obama should provide his original birth certificate.

From a political standpoint, it’s impossible to dismiss the matter as conspiratorial fantasy, akin to, say, claims that the 1969 moon landing was staged. In the latest New York Times-CBS News poll, 45 percent of adult Republicans said they believe Obama was born in another country, and 22 percent said they don’t know. One-third of Republicans said they believe the president is native born.

The same poll a year ago found considerably less suspicion among Republicans. A plurality of GOP adults then said Obama was U.S.-born, and 32 percent said they believed he was foreign-born.

In the latest poll, about half of all independents said Obama was born in the United States. The other independents were about evenly split between those saying he is foreign-born, and those saying they don’t know.

Ten percent of Democrats said Obama was born overseas, and 9 percent were unsure.

Obama’s birth certificate indicates he was born in Hawaii in 1961. Newspaper birth announcements at the time reported the birth, and news organizations’ investigations have rebutted the birthers’ claims. The Constitution says a president must be a “natural born citizen.”

Trump’s leap to the top tier of potential GOP presidential contenders in recent polls has frustrated party leaders who’d like the birthplace issue to go away.

The House’s top Republicans — Speaker John Boehner and Majority Leader Eric Cantor — say they are satisfied that Obama was born in Hawaii. But they have declined to criticize those who state otherwise, and Boehner has said it’s not his job to tell Americans what to think.