This table from a Gallup article on Barack Obama winning women over but as has tended to be the case in recent cycles the marriage gap seems to be at least as big a story as the gender gap. As usual with this question, though, it's hard to say how much of the difference between single and married voters reflects the fact that singles are younger or racial differences in marriage rates.
This article available online at:
http://www.theatlantic.com/politics/archive/2008/06/barack-obamas-lonely-hearts-club/45381/
