The difference is that the the religious right might not vote, whereas the secular left almost always does. The religious right has another hope for the world besides politics. Before Jimmy Carter in 1976 fundamentalists and evangelicals commonly did not vote, especially at the national level. Jimmy Carter created a wedge between evangelicals, who tended to vote for him, and fundamentalists, who still did not vote. In response, Republican activists created the Moral Majority, and found a fundamentalist minister to be their public face, to create a fundamentalist voting bloc.
But the Christian right, and the broader religious right, is still prone to take elections one at a time. They not only decide who to vote for for religious reasons, they decide whether or not to vote at all based on who is running. In 2004 there were 7 million evangelicals who did not vote, according to evangelical pollster George Barna. I thought at the beginning of this endless election that there would be even more this time. With Giuliani, Romney, and McCain the leaders on the Republican side, and no evangelicals of note of the Democratic side, I could see how the most religious voters might just sit out the 2008 election. When Pat Robertson endorsed Giuliani, it was clear that the old Christian right leadership had been absorbed into normal party politics.
And then came Huckabee. Mike Huckabee won Iowa by mobilizing evangelical voters to actually go to the caucuses. If he can do it twice -- say, in South Carolina, or make a big showing in Michigan, where Robertson Christianized the local GOP in the '80s, those 7 million missing voters might come back and vote after all.