I don't think he is, a gave a couple reasons why here: https://news.ycombinator.com/item?id=16099356

But this has been a big topic of debate on his podcast subreddit as well. I think it mainly comes from the guests he has on, but Joe has written on Twitter about how getting left leaning guests on to talk politics is just a lot harder. Russell Brand is great and all, but no one else really seems interested for whatever reason.