"Courage" or "Flip-Flopping?"

Read this article reported by Yahoo and decide whether you think Senator Schumer has great courage or is a flip-flopper/panderer.

The jist of the article is that Schumer, the senior senator from New York, has officially changed his long-tome stance on gay marriage. Whereas he long opposed it, he now magically supports it. Even a professor at the University of Massachussetts admits that "at this point we have a fair amount of knowledge that supporting gay marriage in the Northeast is not the kiss of death politically" and that this is a politically savvy move, not one of courage. If he were really fighting for a principle he would have done it when it wasn't popular.

Now, I have no problem with a politican changing his mind when he can give a good reason for the change. But Schumer gives no such explanation, leaving us to assume the obvious: his polling data once again told him what to think.