Some corporations have been accused of having a "glass ceiling," an invisible barrier that prevents women and minorities from rising to the topmost positions. In that sense, American politics clearly has a "stained-glass ceiling," a de facto barrier to atheists running for office. Despite the many great Americans who've been nonbelievers, despite the guarantees of secularism written into our Constitution, outspoken atheism is still seen as an insurmountable liability for anyone who seeks to serve our country as an elected officer of the government.
True story: once, a co-worker was shocked to hear I was an atheist. "But...you're so nice to people!" she said. "And you take such good care of your cats!" It astounds me how many people think that atheism renders a person incapable of being honest, kind, responsible, or empathetic.
I can't wait for the day that a political candidate is accused of being an atheist, and responds with "Yeah, so what?" And still gets elected.