Citizen Reform has a success story in Georgia:

Poorly funded physician Paul Broun Jr. scored a shocking 50.4% victory over former state Sen. Jim Whitehead, the establishment's consensus favorite. Columnist Robert Novak says Dr. Broun's victory has "terrified those incumbent Republican House members who had thought themselves safe for re-election in 2008" primaries.  

Dr. Broun prevailed by using direct mail and telephone messages to go over the heads of party leaders with a pledge that, once in Congress, he would apply a four-way test before voting on any bill:

1.  Is it constitutional and a proper function of government?

2.  Is it morally correct?

3.  Is it something we really need?

4.Is it something we can afford?