Money and results

So what did the $6 billion spent on the various campaigns actually buy?  I have a hypothesis that I hope some energetic researcher will test: that the strong showing by Republican House candidates came in part from advertising by Super PACs and other unaffiliated groups.  It's surprising to me that so many Tea Party radicals won reelection. Redistricting helped, of course, but I wonder whether many incumbents were saved by the outside money.