With Jon Huntsman announcing his candidacy for the Republican presidential nomination, Mitt Romney is no longer the only Mormon in the running. Both candidates have the potential to become front-runners in the race, even though a recent Gallup poll shows 22 percent of the nation would not vote for a Mormon.   Mark Silk, director of the Leonard E. Greenberg Center for the Study of Religion in Public Life at Trinity College, says Romney's past failures in presidential races were in direct correlation to his religion. Helen Whitney, the producer of the PBS documentary, "Mormons," believes American's fear of Mormons has died down a bit as people understand the religion and its people more.