Why is Ron Johnson behind in Wisconsin?

According to the RealClearPolitics polling average, Ron  Johnson is still pretty far behind Russ Feingold.

I would have thought that he’d be doing much better, due to (a) the Project Veritas video that shows Scott Foval bragging about sending thugs to a Scott Walker rally (b) the same Scott Foval saying that half of Iowa is racist as f**k, and Wisconsin isn’t any better, and (c) Scott Walker.

What gives?  Why isn’t Johnson winning this?