Nate Silver, über-pollster, comments,
At the same time, it is probably also no longer safe to say that opposition to same-sex marriage is the majority position, and it is becoming dubious to call it the plurality position. Opinion on the issue, instead, is close to evenly divided, with results varying somewhat depending on things like question wording. It may be noteworthy that CNN tends to find slightly higher levels of support for gay marriage with a question that is explicitly framed around constitutional rights, echoing arguments that are very much at the center of the ongoing legal case against California Proposition 8
And in a separate piece, Silver provides a graph of the long term trends. The rate of acceptance is increasing faster. That is, over the last year or so, people have moved to our side at about 4%, whereas in previous years it was a steady 1% or so.
It's not over, but is the tide turning?
Data from 538.com