Have you ever wondered why you never hear about the percentage of evangelical voters who vote Democratic? Think about it. You hear all the time about what percentage of Republicans voters are evangelical Christians, but never a discussion about what percentage are Democratic. That's because, according to this NY Times article, the exist polls don't ask that question.
This is a quote from the article:
If you want to know what percentage of voters in the Republican caucuses and primaries described themselves as born-again or evangelical Christians — and whom they voted for — exit polls will tell you. If you want to know what percentage of voters in the Democratic caucuses and primaries consider themselves born-again or evangelical Christians, well, sorry. No one knows.
No one knows because the exit polls did not ask
Here's why they don't ask:
Let’s be clear. Exit polls cannot ask about everything. The questionnaires handed voters hurrying away from polling places cannot be any longer than two sides of a single sheet of paper. Pollsters have to make choices. And representatives of ABC News, CBS News, CNN, Fox News, NBC News and The Associated Press, who have formed the National Election Pool that has conducted state and national exit polls since 2003, have good reason to be tight-lipped about what goes into making those choices.
Interestingly enough both progressive evangelical Christians and Howard Dean are raising the point that since exit polls don't seek this information, the media doesn't cover the story of evangelical Democrats. This leads to the situation where most people think that Christians, especially evangelical Christians, only support Republicans.
This, of course, is not true. According to the CNN exit poll for the 2004 election, 23% of 2004 voters said that they were evangelical voters. Of those, 21% voted for John Kerry. Since there were over 112 million Americans voting, 21% of voters represented a lot of voters, indeed over 21 million of them.
This lack of balance in reporting voting by evangelicals may result from more than just a lack of space on a questionnaire. My guess is that very few reporters who cover national politics, or their editors, know many evangelical Christians. Therefore, given the attention that the Republican Party pays to evangelical Christians, it is easy for them to assume that evangelical Democrats don't exist.
News coverage represents the decisions that are made by reporters, editors, and publishers. Those decisions are governed by the background that these decision makers bring to the process. If their background is such that evangelical Christians are all lumped together as Republicans, their decisions will reflect that fact.
The problem isn't that America is diverse, the problem is that decision makers in the news industry may not be diverse, not only racially, but culturally.