The problem is, we rarely "shape" the party in the primaries, unless of course the primary is open. Knocking off an incumbent Republican is occasionally possible at the State Legislative level; at the Congressional level it fails 99% of the time.
I know of one organization in Texas that specifically focuses on Republican primary elections, Heritage Alliance. If we are serious about this kind of thing and wish to pay it more than just lip service, many more of these organizations are needed. I can tell you that the head of Heritage Alliance PAC is among the most feared and reviled men in the Republican Party (one of the reasons I like and respect him), because he foments vicious intra-party battles in primaries which officeholders have a tendency to believe are mere formalities on their way to another election victory. Even a close race can cause a self-interested politician to change his ways.
But this costs money, and a lot of it. Are Republicans prepared to do this - to risk splitting their party in the primary in order to put conservatives into general elections? Or when Republicans say, "The time to change the party is in the primaries, not the general" are they just trying to keep Republicans on board, safe in the knowledge that nothing will really change in the primaries?
What say you?
I say, if you can't change the Republican Party in the primaries, you have no chance of creating, and empowering, a new party. I'll take the presidencies of Ronald Reagan and George W. Bush over the self-righteous, warm fuzzy of being a member of a "pure", but powerless, party any day of the week.