Texas Gov. Rick Perry, struggling to claw back to prominence in the race for the U.S. Republican Party's presidential nomination, is renewing the so-called birther issue, suggesting in a new interview he harbours doubts that President Barack Obama was born in the United States.

"I don't have any idea," Perry told Parade magazine when asked whether he believes the authenticity of the long-form birth certificate Obama released in April, largely to silence real estate mogul Donald Trump's claims that the president wasn't born in the U.S.

"I had dinner with Donald Trump the other night," Perry said. "He doesn't think it's real."

When the Parade interviewer reminded Perry that he's actually seen Obama's birth certificate, Perry replied: "I don't know. Have I?"

Racist undertones

Perry's sympathies for the birther cause have emerged at a dangerous time. The collection of right-wing conspiracy theorists who claim Obama is unlawfully holding office because he wasn't born stateside have recently begun flinging accusations at two high profile, non-white Republican politicians.

The hysterics over Senator Marco Rubio of Florida, the son of Cuban immigrants who's widely touted as a possible vice-presidential nominee, and Bobby Jindal, the governor of Louisiana, suggest the cause isn't fuelled by partisan politics, but something more sinister.

Charles Kerchner, a plaintiff in a lawsuit that claims Barack Obama was not born in the United States, recently obtained the naturalization petitions of Rubio's parents, who emigrated to Miami from Cuba in 1956. The Rubios didn't become citizens until 1975, prompting Kerchner to assert the senator would be ineligible to be president since his parents weren't U.S. citizens when he was born.

"Senator Marco Rubio is not a natural-born citizen of the United States to constitutional standards," Kerchner wrote on his blog. "He was born a dual citizen of both Cuba and the U.S.A. He is thus not eligible to serve as the president or vice-president."

Same goes for Jindal, the son of Indian immigrants, Kerchner said.

"Jindal is NOT a natural-born citizen of the United States," Kerchner wrote. "His parents were not U.S. citizens when he was born."

Constitution doesn't define term

Rubio's office told Florida's St. Petersburg Times that the senator considers himself a natural-born citizen because he was born on U.S. soil. The U.S. Constitution, in fact, fails to define what is meant by the "natural-born citizen" requirement for the presidency. Arizona Senator John McCain was born in Panama, for instance, yet never incurred accusations about his eligibility for the White House when he ran for president against Obama in 2008.

The birther's new tactics have proven they aren't fuelled by party politics, the Washington Post's Dana Milbank wrote on Sunday, but are attacking politicians based on their race. He urged Republicans to distance themselves from the "angry and unstable in their ranks."

"Now that the birthers have begun to eat their own brightest prospects, perhaps Republican lawmakers will finally feel compelled to say something," he said in a piece written before Perry's remarks became public.