The regligion of those who vote Democrat is mostly atheism,
I'm not sure what you are trying to say here. I think the demographics would show that the vast majority of people who vote DIM would describe themselves as religious people, as opposed to secularists.
Less than 10 percent of Americans call themselves atheists. I haven't seen a poll on those who call themselves "secularists" but I wouldn't be surprised if most of the Dem votes should term themselves such.
So it seems pretty safe to say that secularists vote Dem.