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Voter turnout and vote choice of evangelical Christians

Mark Palko writes, “Have you seen this?”, referring to this link to this graph:

I responded: Just one of those things, I think.

Palko replied:

Just to be clear, I am more than willing to believe the central point about the share of the population dropping while the share of the electorate holds relatively steady, but having dealt with more than my share of bad data, I get really nervous when I see a number like that hold absolutely steady.

My response:

I did a quick check of some of those 26% numbers online and they seem to be from actual exit polls. Them all being equal just seems like a coincidence. The part of the graph I really don’t believe is the sharp decline in % evangelical Christian. I’m guessing that the survey question on the exit polls is different than the survey question on whatever poll they’re using to estimate % evangelical.

And, since I have you on the line, here are some graphs from chapter 6 of Red State Blue State:

It seems that religious affiliation is becoming more of a political thing. Or maybe political affiliation is becoming more of a religious thing.

In any case, be careful about comparing time trends of survey questions that are asked in different ways.


  1. Marin says:

    “…they seem to be from actual exit polls.”

    so how valid are such exit polls?

    what’s the typical Non-Response Rate for such “actual” exit polls?

    • Andrew says:


      Exit polls have big, big problems. But here the question was not about any particular one of these polls, but rather the stability of the 26% in contrast to the decline in the other curve. My point in saying that I checked the exit polls online is not that I believe the 26% (but I’m guessing it’s not too far off, conditional on how the question was asked) but rather that I checked this to rule out the possibility that the graph was just a data goof, along the lines of Reinhart-Rogoff or this example from a few years ago.

  2. Dan F. says:

    There may be simple explanations for why the percent identifying as white evangelical Protestant would drop. For example it could be that for cultural reasons internal to such contexts these people have decided not to label themselves “evangelical” or “Protestant” or “born again”, some other label having become popular. Certainly such explanations need to be explored.

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