1) Acting out of strength

The Democrats are in a really strong position this year.  When we're winning in MS and AL, that's a sign that we're likely to extend our majority.  To the degree that this effects November, it'll be a question of how much does it cut into our gains, not how much does it kill us.  That by itself is a reason to not fear.

2) Redundancy

If there's one thing we've learned about the press over the past few years, it's that they get bored.  Ask them to cover the same story over and over again and they'll start to look for an excuse not to.  

It's not just the press that gets bored; it's also an issue with voters.  When you keep bringing up the same allegedly scandalous point over and over again, it starts to lose its effect.  That's horrible when it comes to (say) the violent nature of war, but here it works to our favor.  After three elections on this topic, the, "OMG NO!!" factor is wearing off.  The underlying questions about why we allow this inequality to continue has more of a chance to be heard after the shock factor has worn off.  And the fact is that without that knee jerk aversion, it's hard to argue that there's a problem here.

Not only does the repetition make people more blasé about the damage this may cause, but it also means that there's less potential for it to affect the general election.  There's no swing states left to try to get initiatives drives going.  They all passed them in 2004.  This is likely to stay localized to California.

3) The McCain Factor

This one may be huge.  McCain is opposed to amending the constitution on this oh so important issue.  It's hard to get people out in droves to vote for a candidate on social issues when he doesn't agree with them himself.  Not only is this not likely to help him, it could actually do him damage if he doesn't handle it correctly.  

McCain has the choice of sticking to his maverick ways and driving a bigger wedge between him and his base or selling his views out and increasing the connection between him and Bush.  I'm assuming he's going to try to stick to the former, but in doing so, it'll make more social conservatives wonder what the difference between him and Obama is.

4) Larger issues

The economy is looming large, very large.  Gas prices are terrifying people.  Iraq can be spun into that picture.  With such stark differences on how to deal with these, there's a real chance that we can marginalize this issue more than we could in past years.

Again, we shouldn't support civil rights based on political expediency, but it's nice that the timing came together as well as it did.  Sure, we'd all be happier if this ruling was made in 2009, but at some point it would give people an issue to run on.  If we can get past this election, we might not only have a major gain for equality in this country, but we might destroy a wedge issue and further diminish the Republicans as being a party stuck in the past.