Perhaps he's not doing as well as we think he is...
I certainly hope he isn't but I really cannot see any other reason for him to take a hard left tack like he has. If he were that far out front he shouldn't need to keep the MooreOn.org/KOS kooks corralled and he could mollify the independents with the soft platitudes that make them gurgle and coo. There is a reason politicians do things and someone with a 16 point lead does not run to the base like this that is what primary elections are for.