There are actually a lot of surveys that show that liberals have an IQ about 10 higher than conservatives and that atheists have an IQ 14 higher than theists.
I've heard that liberals have 2x the number of atheists as a % than conservatives.
Once you get over the silly idea that there's a magical man in the sky demanding you follow ancient superstitious rules about stuff, you generally start to realize that as long as what people do doesn't harm others, there's no reason they shouldn't do it if it makes them happy.
I do personally, however, tend to be a bit fiscally conservative...which in the US means Democrat, not Republican, because the Republican "voodoo economics" of supply-side crap is what got us in this horrible deficit hole.
I tend to be liberal on domestic and social issues and more conservative when it comes to foreign policy issues. I hate both the democratic and republican parties though.