The anti-Mormon bias closely mirrors the 17 percent of respondents who said they would not vote for a Mormon in 1967.
Gallup has conducted the same poll eight times, generally each time a Mormon was running for president -- during the 1968 campaign of George Romney, the 2000 campaign of Orrin Hatch, and in 2008 and 2012 during Mitt Romney's campaign. The percentage of voters surveyed who said they would not vote for a Mormon candidate averaged 19 percent over time, the highest being 22 percent last year.
Democratic voters expressed more of an anti-Mormon bias, with 24 percent of respondents against a Mormon candidate who is otherwise well qualified, whereas only 10 percent of Republican voters seemed to have a problem with a Mormon candidate.
Gallup surveyed 1,004 registered voters over the age of 18 between June 7-10 over the phone. The margin of error is plus or minus four percentage points.