I think there's actually a majority in favor of civil unions, and many of the civil rights attendant to (no pun intended) marriage. I wasn't just talking about California (apologies), and the national polls I remember had rather large majorities opposed to gay marriage, when the magic word itself was used.

People against gay marriage are not necessarily the dupes of the religious right simply because they happen to take the same position, and there isn't a vast religious conspiracy to suppress gay marriage. It's just that many people, sadly, are still a bit uncomfortable with gay marriage. The enemy of my enemy is not necessarily my friend, and politics really does make strange bedfellows.

Yes, there isn't only one party, and there are some very substantive differences between Bush and Kerry on gay rights. However, just as I'm more angry at Bush than Kerry for failing to cut government spending (he's the Republican, and purported "fiscal conservative" [HA!]), I'm more angry at Kerry than Bush for failing to support gay marriage explicitly (he's the Democrat). No, there isn't just one party, but there is just one tactic: take your base for granted, and tack to the mushy middle to make yourself look safe for swing voters.