No, he's not. Obama had his finger in the wind, and the wind was blowing in favor of Prop 8. Hence, his comments on marriage and God.
But there was his base to keep in line. Thus, his libertarian-seeming opposition to codifying traditional marriage in the state constitution, which is what Prop 8 attempted to do. He was clearly trying to have it both ways: Give the Christians a warm feeling about him while reassuring the base.
A month or two before his Rick Warren encounter, Obama had written in a letter to the Alice B. Toklas LGBT Club:
As the Democratic nominee for President, I am proud to join with and support the LGBT community in an effort to set our nation on a course that recognizes LGBT Americans with full equality under the law. That is why I support extending fully equa! rights and benefits to same-sex couples under both state and federal law. That is why I support repealing the Defense of Marriage Act and the "Don't Ask Don't Tell" policy, and the passage of laws to protect LGBT Americans from hate crimcs and employment discrimination. And that is why I oppose the divisive and discriminatory efforts to amend the California Constitution, and similar efforts to amend the U.S. Constitution or those of other states.
His support for traditional marriage has since "evolved" as he has "grown in office". Of course, what really happened was that the political winds shifted during his first term, such that he felt comfortable going fully with his true feelings for 2012.
Rand Paul:
"Preaching to the choir is not working for the conservative movement. We are growing stale and moss-covered. We must evolve, adapt or die."
"I think that the Republican Party, in order to get bigger, will have to agree to disagree on social issues,"
"The Republican Party is not going to give up on having quite a few people who do believe in traditional marriage. But the Republican Party also has to find a place for young people and others who don’t want to be festooned by those issues."