Reply #9: Exit poll, by religion:

[muriel_volestrangler]

Vote by Religion
           Total  Yes  No
Protestant (43%)  65%  35%
Catholic   (30%)  64%  36%
...
None       (16%)  10%  90%

http://edition.cnn.com/ELECTION/2008/results/polls/#val=CAI01p2

And if you look at the figure for how frequently people attend church, the difference is even more marked. Yes, religion, in particular organised religion that campaigned for the proposition, has a hell of a lot to do with this - and that's what the campaign itself says: http://ap.google.com/article/ALeqM5hZmLBrL36NObNyMR0ghXN7vB5hYwD94ADAB80