I always suspected it!
http://www.gc.cuny.edu/faculty/images/image040.gif
Most of course claimed to be independent or gave no answer to this question. But it does seems significant that of those who answered (probably largely marginal members, inactive or disfellowshipped/disassociated) five times as many identified themselves as Democrats than as Republicans - making them perhaps the most "liberal" denomination, politically speaking, in the US.
It also seems to me that apart from a few of the awkward squad, if those on this board are anyway representative, apostates tend to be fairly liberal in outlook too.
Mormons are overwhelmingly Republican - no surprises there either.
The figures for race are interesting too:
http://www.gc.cuny.edu/faculty/images/image037.gif
Blacks are better represented among Jehovah's Witnesses than any other major religious group in America.
And 0% of Mormons identified themselves as black.
This has probably been discussed before, but it is new to me. The whole thing is interesting:
http://www.gc.cuny.edu/faculty/research_briefs/aris/key_findings.htm
Slim