You did not misread that headline.
Of course Obama doing the right thing in embracing the idea of marriage equality will help fire up the LGBT community and the broader progressive base. It may well inspire more people to volunteer and to contribute, and I have been arguing for years about how important it is for the president to unify and motivate his base, and this definitely helps him do that. But let's face it: Mitt Romney is so far over the hill with his far right-wing supporters that he was never going to win many LGBT or progressive votes anyway. Obama has always been the overwhelmingly obvious pick for pro-gay rights folks. This decision may inspire a few more disaffected voters in those communities to go vote, but the number of new votes he picks up here is pretty small.
Contrary to conventional wisdom, this does help him with swing voters, though.
Here is what I believe to my core, based on 30-plus years in politics, about the way people decide who to vote for: character and values matter more than most issues. There are some mega-issues, like the economy and Social Security, that are more important than others in determining how people vote, but even on those issues the claims and counter-claims get confusing, and voters ultimately decide more on who they trust and respect than on their stand on a specific issue. Issues, and how a candidate handles the issues, becomes a proxy for voters' judgments about their character. And swing voters don't mind disagreeing with candidates on issues, they usually assume that they will on some of them, but if they look weak in the way they handle them, it makes people uncomfortable about their character. When a candidate waffles, or it feels like they are trying to be cute on an issue, voters start asking themselves: are they weak? Are they a liar? Do they have no moral core, or lack strength and resolve and toughness?
I first noticed this in the 1984 Reagan-Mondale race, where the exit polls and other post-election surveys were startling: people agreed with Mondale over Reagan more than 70 percent of the time on the issues, and knew that they disagreed with Reagan a lot. But they thought he was stronger, they trusted him more. I've noticed similar trends in several elections since, in Bush vs. Dukakis, in George W. Bush vs. Gore and Kerry. How people decide who to vote for is a complicated stew, but they don't mind supporting a candidate they disagree with on some issues if they think one candidate has better character.
Here's the other important thing: voters have been convinced for a long time that Obama and other Democrats are pro-equality, but just didn't want to admit it. Starting in the early 2000s, I started noticing in focus groups and other chances to hear what swing voters were saying that they generally assumed, no matter what the candidate was saying, that the Democrats were pro-marriage equality and the Republicans were against it. It bothered many of these voters that the Democrats wouldn't admit it because they felt they were being lied, they felt they were being typical politicians. Obama coming out clearly in favor of gay marriage shifts that character question in his favor.
The fact is that being against gay marriage is not a priority voting issue for very many people, and for those that it is, they are mostly already voting for Mitt Romney. Swing voters will vote based on two things: character and economics. Obama's clear decision on this issue shows his strength, his honesty, his courage, and so will win him real points on the character side of the equation.