Reagan's success was driven by the defection of evangelicals from Carter's camp. Although they favored Carter by 21 points in a Gallup poll two months before the 1980 election, many began to feel that he had drifted too far to the left. Two-thirds of white evangelicals ultimately cast their ballots for Reagan.
Yet a striking thing happened. In 1984, Democrats did not make a serious bid to win back religious voters. Instead, they nominated Walter Mondale, Carter's vice president, who never brought his faith into the public sphere. To the contrary, he told voters that politicians should keep their "nose out of religion." Reagan, running his Morning in America campaign, handed Mondale the most devastating electoral college defeat in American history, 525 to 13.
The demographics remain abundantly clear. Even though religiosity is dropping in the U.S., according to the Pew Center, more than 70% of Americans still consider themselves Christian, and about 6% follow other faiths. Republicans have vigorously pursued religious voters since Carter's day, and whenever the Democrats have run candidates uncomfortable with the language of faith, they have been defeated.
Michael Dukakis, Al Gore and John Kerry were all privately religious, but they did not justify their positions through religious morality or references. By contrast, the two Democrats since Carter to secure the White House were adept at using their religious worldview to connect with voters. Bill Clinton often deployed Scripture to reinforce his arguments about poverty, while Barack Obama famously saved his candidacy with a speech tracing America's present racial discord to the "original sin of slavery."