It seems the answer is that those who identify themselves as "strong" pray the most regardless of party affiliation. Not what you would have expected? I don't know enough about the survey to comment but it would be interesting to find out more about the content of the prayers. Who are they praying too? What are they praying for? What do they consider prayer? I don't pray to a guy in the sky because I don't believe there is a guy in the sky. But on a regular basis I do meditate and I do voice petitionary prayers on behalf of people. If I were asked if I pray regularly I would say yes but I would imagine that my prayers would look different than someone who is more conservative. What do I, a strong Democrat, have in common with a strong Republican? We are not lukewarm in our beliefs; we think our thoughts, deeds, intentions, and prayers make a difference. Just my guess.
Here, by the way, is the best comment to this graph on the site:
Well, here is something kinda weird. I’m an atheist, but I occasionally pray. Probably this phenomenon can be explained from my growing up in a family that was (very casually) Christian. I generally start out with something like “Dear God, if you do in fact exist (contrary to my best judgment)…”
I only pray on behalf of friends or relatives who are sick, when I have to fly, or when the lottery goes above $100 million.
I am not only a bad Christian, I am also a pretty lame atheist.