Let's hope you're so particular when it comes to Trump and his campaign promises. So far his "draining the swamp" means he's filled it with establishment sewage. http://www.cnn.com/2016/11/10/politics/donald-trump-transiti...

He lacked sufficient Congressional support for a lot of that. And when he did release detainees? He was demonized by many (particularly from the right).

Closing Guantànamo Bay turned out to be much more difficult than Obama assumed. The full sordid story can be found here:

http://www.newyorker.com/magazine/2016/08/01/why-obama-has-f...

I agree with the overall message that Obama was way more establishment than he made himself seem in the campaign, but Guantanamo is a horrible example. He's consistently brought it up and fight for it, if it was an empty campaign promise he would have quietly never mentioned it again.

Impossibility can mean a couple of things - the logistical challenges of where Guantanamo prisoners should go, and the impossibility of getting it done in a Republican-controlled senate and house.

The first is in line with your point, although I think it's a reasonable assumption that Obama honestly underestimated the challenge. For the second, it's not reasonable to call it a broken promise if he made a good faith effort and was blocked by something out of his control (that he couldn't have necessarily predicted)