A recent Pew poll found that while 78 percent of evangelicals voted Republican in 2004, only 57 percent were inclined to vote for Republican candidates this fall.
He may not be on the ballot, but the word of God could influence millions of voters on Tuesday. About 20 million of them are considered a critical part of the Republican base.
"All of us need to vote our values, especially those states that have marriage amendments on the ballots," said Tony Perkins, president of the Family Research Council.
But some evangelical moderates are igniting a new debate about faith and politics, urging their flocks not to vote any party line.
"Our faith should be fiercely independent and the thorn in the side of all the politicians," said Jim Wallis, a popular speaker and editor in chief of Sojourners, a magazine about faith and culture.
Monique el-Faizy, author of "God and Country: How Evangelicals Have Become America's Mainstream," believes that evangelicals are becoming disenchanted with the party as well.
"They feel the Republican Party isn't addressing those concerns that increasingly they see as important moral issues," she said.
Lisa Baker, an evangelical Christian from a devoutly evangelical Republican family, works to help her Sunday school students understand the teachings of Christ -- something she thinks Republicans are forgetting about these days.
"Not only on the issue of Iraq, but particularly because in our country, now more and more, there is a deeper dichotomy between rich and poor," Baker said.
At Wheaton College in Illinois, a top evangelical university, professor Lindy Scott surprised many when he ran for Congress as a Democrat earlier this year.
"I think there are some students [and] faculty who would definitely vote Democratic this time … for the first time," Scott said.
Many young evangelicals like Ben Lowe, a student at Wheaton, think of the environment as part of God's creation and think that it is just as important as abortion as a litmus test.
"The environment would be one of those areas where you could say we've almost had … generally speaking … a blind spot in the evangelical church," Lowe said.
Baker is taking a stand. She plans to vote for the Democrats next week and is even accusing the Republican right of fear-mongering.
"To me it's such a threatening kind of stance. … If you don't get on board with us about anti-gays or gay marriage, the family will be ruined," she said.
Still, Baker may be the exception.
"Being disillusioned with the party and walking into a booth on Election Day and pulling a lever with a D next to it are very different things," el-Faizy said.
Experts predict most disillusioned evangelicals may be more likely to just stay home.
If even 10 percent of them do, that could make a critical difference at the polls.