Jon Terbush February 15, 2011, 12:59 PM

The theory that President Obama is not a natural born U.S. citizen (and thus ineligible to be President) has hardly been squelched. According to a new PPP poll, it’s actually a predominant belief within the Republican party.

In the poll, 51% of all likely Republican primary voters erroneously believed that President Obama was born outside of the U.S. Only 28% of those Republican voters said they thought Obama was born in America, while 21% said they were unsure.

Skeptics have been crying shenanigans since long before Obama’s inauguration. Obama, the son of a Kenyan immigrant, has produced his Hawaiian Certificate of Live Birth as proof of that he was born in this country. Yet conspiracy theories continue to abound, leading some to doubt Obama is eligible to be president.

While half of all Republicans think Obama is not a natural born citizen, that belief is more commonly held in the party’s most conservative quarters.

The poll asked Republican voters for their opinion of a slate of contenders for the party’s presidential nomination. Voters who expressed a favorable opinion of the more conservative candidates were more likely to say Obama wasn’t born in America.

For example, among the two-thirds of likely Republican primary voters with a favorable opinion of former Alaska governor Sarah Palin, 83% said Obama was not born in the U.S. Yet among the minority who viewed Palin negatively, 52% said they thought Obama was born in America.

Birtherism continues to dog Obama two years into his presidency, and he’s getting little help from GOP lawmakers in putting the issue to rest. In a recent interview, House Speaker John Boehner (R-OH) said that, while he believes Obama is a citizen, he’s not going to go around telling other people to think the same way.

The PPP poll was conducted February 11-13 among 400 Republican primary voters nationwide. It has a margin of error of 4.9%.

Barack Obama, Birth Certificate, Birther, PPP, Polls, Republicans