GOP's Hold on Evangelicals Weakening

"The allegiance of evangelicals has been more in flux over the past 12 months, suggesting that the considerations going into their votes are changing," said Scott Keeter, Pew's director of survey research.

In addition to the war and congressional scandals, those considerations may include a broader definition of religious issues. Some influential ministers, such as the Rev. Rick Warren, author of the bestselling "The Purpose-Driven Life," are urging evangelicals to fight poverty, safeguard the environment and oppose torture on biblical grounds.

To the extent that evangelicals now view these issues as "matters of conscience" alongside abortion and same-sex marriage, they could shift some votes into the Democratic column, said Ron Sider, head of the group Evangelicals for Social Action.

Another factor in evangelicals' changing loyalties may be the efforts of Democrats to reach out to them. In Michigan, evangelical pastors helped write the preamble to the state party's new platform. "Democrats in this state are seeking the Common Good -- the best life for each person of this state. The orphan. The family. The sick. The healthy. The wealthy. The poor. The citizen. The stranger. The first. The last," it says.

But before Democrats take credit for the shift, they might ponder one of the findings in a recent survey of 2,500 voters by the Center for American Values, a project of the left-leaning People for the American Way Foundation: Republicans have lost more support (14 percentage points) than Democrats have picked up (4 points) among frequent churchgoers.

That rings true to Michael Cromartie, an expert on evangelicals at the Ethics and Public Policy Center, a Washington think tank. "Erosion for evangelicals doesn't necessarily lead to Democratic voting. It leads to nonvoting," he said.

Republican strategists are hoping the drop will prove temporary.

"There is a dip in support for the GOP among religious conservatives, no question," said Leonard Leo, head of Catholic Outreach at the Republican National Committee.

"People of faith were disaffected over the summer, but I think they'll come back," he added. "It's like any other election season -- people get frustrated that they haven't achieved everything they want. But as you get close to the election, you begin to look at the alternatives and realize that staying home is going to make things worse rather than better."