Although it is interesting where this 10% support is coming from and where it ends up. He was in the 1-2 range this time four years ago.
The latest Fox poll is instructive. It has Trump vs. Clinton with Trump 45, Clinton 42. The same poll with Johnson added is Trump 42, Clinton 39, Johnson 10. Trump has a 3% lead either way. No difference. Johnson takes equally from Pubs and Rats.