Instead of merely handing out endorsements, these groups are spending big on expensive advertising campaigns on behalf of their favored candidates. They’re quietly circulating opposition research raising questions about tea-party challengers’ fitness to serve. And they’re even airing positive testimonials—an approach once considered the domain of the candidates themselves, not outside groups. (The New York Times reported that more than a quarter of the ads from super PAC American Crossroads so far this cycle have had a positive spin; not a single one did in 2012.)

McConnell former Chief of Staff Billy Piper says that McConnell learned from two veteran Republican senators who managed to beat back conservative opposition with aggressive tactics. In 2010, John McCain won decisively by raising big money, moving to the right on immigration, and casting his opponent—former House member and talk-show host J.D. Hayworth—as out of the mainstream. Two years later, Orrin Hatch attacked outside conservative groups that attempted to paint him as a moderate, winning two-thirds of the GOP primary vote against an opponent backed by the tea-party group FreedomWorks.

“It’s a good lesson, one that McConnell certainly noticed. It fits in with his mode of campaigning: very aggressive, getting involved early, making sure no one is successful at defining you,” says Piper, now a lobbyist whose shop maintains close connections with Senate Republicans. “Nobody likes family squabbles, but at the end of the day the goal is to produce candidates that can win in the fall. The Chamber has been a leader to make sure we can accomplish that result. I don’t think anyone looks at the last couple of cycles and thinks we did a very good job generally. Something had to change, and they had the courage to step up and do what was right.”