Video Clip to the ABC News interview (some reason, can't embed it).
Money quote: "I have to tell you that over the course of several years as I have
talked to friends and family and neighbors when I think about members of
my own staff who are in incredibly committed monogamous relationships,
same-sex relationships, who are raising kids together, when I think
about those soldiers or airmen or Marines or sailors who are out there
fighting on my behalf and yet feel constrained, even now that 'Don't Ask
Don't Tell' is gone, because they are not able to commit themselves in a
marriage, at a certain point I’ve just concluded that for me personally
it is important for me to go ahead and affirm that I think same sex
couples should be able to get married."
For the most part, this doesn't change much in getting voters to switch to Obama's side come November: people who hated on Obama already were also hating on Teh Gay.
But what this does do is excite the Democratic base and independent voters (and disaffected Republicans) who are pro-civil-rights. It's one thing to be voting AGAINST someone (it's very easy to despise now-established Romney and the current Republican Party as a bunch of bullying lying scumbuckets), but it's a lot more satisfying to be able to vote FOR someone.
And Obama is making it very easy to vote FOR him. It's not just for marriage equality: I've been impressed with Obama's move on women's issues such as getting the Ledbetter Fair Pay Act passed, nominating a sizable number of women to key government positions (including two women to the Supreme Court, bringing that just body to reflect our nation's actual population of men-to-women), standing up for Planned Parenthood when the GOP leadership is trying to outright kill it, getting his Obamacare to lower costs and raise coverages for women, et al.
This is something I've been saying since Obama came out for marriage equality: this isn't so much a pro-gay move as it is a pro-people move. Obama is Pro-People.
And I'm all for that.