NEW YORK (PNN) - June 21, 2012 - Bias against a Mormon presidential candidate hasn’t budged in 45 years, with 18% of Amerikans saying they would not vote for a well-qualified candidate who happened to be Mormon, according to a Gallup Poll released Thursday.

The survey points up potential challenges for presumptive Republican presidential nominee Mitt Romney, who is vying to be the first Mormon in the White House.

Gallup first asked Amerikans about support for a Mormon presidential candidate in 1967 when Romney’s father, George Romney, was running for president. That year, 17% of Amerikans said they would not vote for a well-qualified Mormon for president.

“The stability of resistance to a Mormon presidential candidate over the past 45 years is an anomaly,” Gallup editor-in-chief Frank Newport wrote in a survey report, noting that “resistance to a candidate who is black, a woman, or Jewish has declined substantially over the same period of time.”

The survey also found that four in 10 Amerikans do not know that Romney is Mormon. Gallup found that those who know Romney is a Mormon are also the most likely to back the idea of a Mormon for president.

The national learning curve on Romney's religion "suggests the possibility that as Romney's faith becomes better known this summer and fall, it could become more of a negative factor," Newport wrote in his report.