The Pew Forum on Religion & Public Life put together a slideshow explaining the trends between religious groups and political party identification.
There’s nothing in it you couldn’t have predicted yourself, but here are a few of the highlights:
The “Nones” need to be more like Black Protestants — we’re only about 2:1 in favor of the Democrats while they’re more like 9:1.

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11% of the Republican or Republican-leaning voters are religiously unaffiliated:

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24% of the Democrat or Democrat-leaning voters are religiously unaffiliated — which is why they ought to being paying more attention to us:

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These results can go two ways. First, as long as religious groups dominate both pie charts, we’re not giving either political party a great reason to pay attention to us. On the other hand, when religiously unaffiliated voters make up a quarter of the Democrats’ audience, they ought to be far more inclusive of us than was evident in their speeches at the DNC.