The marriage gap  is always a low priority when news websites put up their exit polls. Everybody knows that's not an important gap, not like the colossal gender gap, so nobody pays attention to it, so next time, the marriage gap isn't give much play either, and so forth and so on forever and ever amen.
After checking a number of outlets, I finally found that the Washington Post has an elegant exit poll demographics page  that does have the data.
Romney v. Obama
Married Men: 60 - 38
Married Women 53 - 46
Non-Married Men 40 - 56
Non-Married Women 30 - 68
From this, just guesstimating, until somebody puts up the exact numbers:
Marrieds (both sexes): 56 - 42
Singles (both sexes): 35 - 62
So the marriage gap is around 20 points, maybe higher.
In contrast, the famous gender gap was apparently about 9 points, or less than half of the marriage gap.