I don't know... could he have used a series of executive orders to see it closed? I don't think he ever had a fillibuster proof majority to work with on this issue, or if he did, then he didn't push hard enough early on before Republicans, which now have a clearly stated position to oppose and obstruct him at every opportunity, gained greater power in Congress.

That said, if he tries to pin this failure on Republican obstructionism, I am sure the GOP will be quick to reveal the names of Democrats who also wanted to keep Gitmo open.

Lose-lose situation.