I don't think the gay marriage issue cost the Democrats the EV-win. But...

[AP]

...I suspect (without solid evidence) that it seriously padded the Republican popular vote victory by getting a lot of people to vote in the states in which Kerry-Edwards did not campaign.

Gay marriage was going to be a much bigger issue for Republicans. They tried to get it on the ballot in so many more states. It failed and it polled pretty poorly, IIRC, as an issue that was on voters' radar screens. The real battle was in getting people to care more about either terror or jobs/health care/education.

However, gay marriage was probably the thing that got out the conservative Christians in states where Kerry didn't compete. And that did help Bush with a popular vote victory

I'm not sure about Ohio, however.

Maybe it was a big issue in Ohio. Any theories?

[JI7]

1. it did affect Ohio

because Bush got support from people such as the Amish who came out to vote on this gay marriage amendment. Kerry did very well and exceeded goals in GOTV among many groups. but the republicans GOTV in churches had been going on for a few years and the gay marriage thing got them to turnout this time unlike in 2000.

but you are right about it padding bush's popular votes as a result of large turnout in red states to vote on these gay marriage things.