The difference in vote correlates much more with race, age, and church attendance, much more that church or denomination. The causal argument breaks down - evangelical, mega, catholic, baptist, etc.
The problem with megachurches, in the context of my comment, is they tend to die out with their charismatic leader. What I was pointing to was stability of congregation and teaching. Megachurch leaders tend to have their own take or emphasis, Olsteen for example.
Thanks for your reply.
You will find that the evangelical vote will be more conservative than the Catholic in each age, race ans attendance category.
As regards megachurches, I would say that they cannot be broadbrushed, but must be separated by type. The problem with Osteen type churches is that they owe their numbers to a saltless gospel of perfectly pleasing preaching, and others to Benny Hinn type charisma and counterfeits.
Then you have Calvary Chapel types, as well as 57% of megachurches being founded before 1961, in which more legit qualities may be are at work, and often demographics.