For one, there's about 27 universes worth of difference from supporting a specific law which does a specific thing, and supporting a politician who has different positions on different laws. Maybe the other positions he has took priority over marriage equality?
For instance: five years ago, coming out of the economic mess, I'd have prioritized economic recovery (so, someone who knows what they're doing on that front) over marriage equality. That's not to say marriage equality isn't important, but it's all rather pointless if the economy is trashed and everything else goes with it.