It may not have achieved much at all, certainly nothing on freedom of movement, but like previous treaties he could have come back with something.

With a negotiating stance of "they just voted out, what can we give to avoid this?", I am sure some package that didn't compromise the aims of the EU too far, or cost billions, could have been worked out.

Now, whether a second referendum would have swung back to remain, now I'm clueless. :)