Having nothing on your left doesn’t make you leftist. If I drive in the right hand lane and there’s nothing on my left, I am not driving in the left hand lane.

The Alberta NDP under Notley was a centrist party and its policies were far more aligned with the federal liberals than the federal NDP. Obviously, there has been a change in leadership, but I don't see any reason to believe that the Alberta NDP will be any less centrist under Nenshi.