Some Evangelicals Vote Democratic

For the last quarter century, evangelicals have been defined almost entirely as a socially conservative Republican brand. An example of how ingrained this identification is in our thinking is the practice among polling firms to ask GOP voters, but not Democratic ones, if they consider themselves evangelical.
Noted (and overquoted) philospher of science, Thomas Kuhn, describes normal science as being so confident of certain facts that it no longer looks for data to confirm what everybody already knows. So it is with public opinion surveys.
But a research firm, Faith in Public Life, decided to actually ask all voters about their religious preferences:

In the 2008 election, media organizations and pollsters are relying on an outdated script by treating evangelicals as a monolithic voting bloc. The exit polls (sponsored by the major networks, CNN, Fox, and the Associated Press) provide the data for nearly all post-election analysis. Yet, thus far, exit polls have only asked Republican primary voters whether they considered themselves “born-again or evangelical Christian.”
A new post-election poll in Missouri and Tennessee, commissioned by Faith in Public Life and the Center for American Progress Action Fund conducted by Zogby International, demonstrates the diversity of evangelical voters and the need for more thorough polling and careful analysis.

The survey found that not all evangelicals are voting Republican this year:

One in three white evangelical voters in Missouri and Tennessee participated in Democratic primaries.

Also, evangelicals aren't as concerned with the so-called hot button issues associated with the religious right:

In both states, white evangelicals who ranked jobs and economy as the most important issue area in deciding how to vote far outnumbered those who considered abortion and same-sex marriage most important.

It's remarkable what you can learn about people when you ask them what they think.