NEW YORK » Six months after Barack Obama's inauguration, a persistent and noisy legion of doubters won't let go of an already debunked claim—that he is actually a foreign-born, illegal president.

The issue has flared again on political blogs, TV news shows and even a town hall meeting, widely circulated on YouTube, in which a Republican congressman was booed for saying Obama is a citizen.

Mainstream Republicans who want the issue to go away are having a tough time stamping it out as the so-called “;birthers”; resurface, with assists from talk show host Rush Limbaugh and CNN's Lou Dobbs.

Some who had initially dismissed the claim as a laughable political sideshow now wonder whether it's gotten out of control.

“;I've stopped laughing,”; New York Daily News columnist Errol Louis wrote yesterday. “;Too many political and media leaders are deliberately fanning the flames of ignorance and fear, and they should be ashamed.”;

Passions among the birthers run so high that Rep. Mike Castle of Delaware was booed by his own constituents at a recent town hall meeting for saying Obama “;is a citizen of the United States.”; He was responding to a woman who contended Obama was born in Kenya, and shouted out, “;I want my country back!”;

Theories that Obama was born abroad abounded during the presidential campaign, even after an official Hawaii birth certificate was produced, along with August 1961 birth notices from two Honolulu newspapers. Numerous lawsuits and emergency appeals were lodged challenging Obama's eligibility to be president, and all were rebuffed.

The Constitution states that a person must be a “;natural-born citizen”; to be eligible for the presidency. Birthers contend that Obama's Hawaiian birth certificate is a fake, and many say he was actually born in Kenya, his father's homeland.

Limbaugh, for example, joked that Obama and God have something in common—the lack of a birth certificate. Dobbs has broached the issue several times, saying at one point, “;The questions won't go away.”;

And 10 Republican members of Congress have co-sponsored a bill that would require future presidential candidates to provide a copy of their original birth certificate.

The issue also was raised by CNN's Larry King this week, in a conversation with Liz Cheney, daughter of former Vice President Dick Cheney.

“;I think the Democrats have got more crazies than the Republicans do,”; Liz Cheney said. “;But setting that aside, one of the reasons you see people so concerned about this ... people are uncomfortable with having for the first time ever, I think, a president who seems so reluctant to defend the nation overseas.”;

A fellow guest, Democratic strategist James Carville, suggested Cheney should have been more critical of those questioning Obama's citizenship.

“;She refuses to say this is ludicrous, because she wants these people to believe this,”; he said.

Carville is among many Democratic commentators suggesting that Republican officials are reluctant to denounce birthers for fear of alienating an energetic part of their party's base. But even some conservatives say dragging out the controversy only helps Obama.

“;He has a significant number of conservatives wasting enormous amounts of time on a side issue that can never bear any fruit and, as an added bonus, it makes them look somewhat unhinged to many Americans,”; wrote conservative blogger John Hawkins on Townhall.com. “;When your political enemies are making fools of themselves, why stop them?”;

John Feehery, a GOP consultant, suggested Dobbs and other broadcast figures were seeking to capitalize on the controversy to boost ratings.

“;It says more about the media culture we're entering and the decline of responsible journalism, and less about the political realm,”; Feehery said.

Hard evidence has not swayed the birthers, as MSNBC's conservative talk show host Joe Scarborough noted this week.

“;They would rather be like sea lions barking at waves,”; he said. “;Instead of trying to figure out what's happening to their country ... they embrace conspiracy theories, and they make themselves look like cartoon characters.”;