In Obama adviser David Axelrod's new book, he reveals that in 2008 the future president did indeed believe in marriage equality, but he was persuaded by Axelrod and others that it would be too risky to say publicly. So he took the standard Democratic position at the time, in favor of civil unions but against marriage rights.
I imagine that exactly no one is surprised by this. And while it isn't an excuse for deception, the decision should be understood in the context of that historical moment, which is something I get into in my Plum Line post today:
The context of Obama's falsehood is important to understand—both his own thinking and the reception his statements on the matter received. In 2008, the Democratic Party was undergoing a rapid change in its approach to same-sex marriage, and the stated positions of almost every candidate were in flux. Four years before, when the issue exploded into national debate after the Massachusetts Supreme Court legalized marriage equality (their ruling actually came down in late 2003), Democrats scrambled to come up with a position on an issue many hadn't much thought about before. Most of the presidential contenders came down in support of civil unions but against marriage rights, a position that just happened to be where the median voter was. By 2008, that was still the safest position, and the party platform didn't mention marriage equality except to say that the party opposed the Defense of Marriage Act.
By 2008, everyone seemed to understand that the position all the major Democratic candidates were taking was a temporary way-station on the path to an eventual embrace of full marriage equality. Nobody really believed that was where the party and its representatives were going to stay. Half of Democrats supported marriage equality in 2008—up from 40 percent in 2004—but the public as a whole was not there yet. Support for civil unions was a position that was acceptable both to the party base, who knew it was only a matter of time before their leaders "evolved," and to the general public, which was undergoing its own evolution.
Was all that a spectacle of political cowardice? Absolutely. But it's hard to say that anyone in either party had many illusions about where it would end up. To no one's surprise, by 2012—when a majority of the public now supported marriage equality— the Democratic party platform embraced it, as did nearly every elected Democrat from President Obama on down.
As I note, the Republicans are undergoing their own possibly-sincere evolution on the topic. And I'm really interested to hear from Hillary Clinton to see how she'll describe 2008. Like Obama, she was for civil unions at the time and came out for marriage equality a few years later.