For just a few example: a few months ago, back in July, he was in London where he spoke at a rally on behalf of an anti-Muslim activist. After the white supremacist rally in Charlottesville, he pushed a far-right conspiracy theory that the event was a left-wing plot financed by George Soros who had "turned in his own people to the Nazis." Gosar is also an outspoken opponent of the Dream Act, given certain undocumented aliens a path to citizenship. And much, much more.
He represents what is considered a very safe seat in a rural area of west Arizona. But that hasn't stopped his opponent Dr. David Brill from trying, and running a series of eye-opening ads.
As I said, the Democrats have put together a series of these ads. Here's another which uses some of the same material, but goes into more political depth.