The titanic member-versus-member clashes have been the House primaries to watch so far this cycle, but four other incumbents have already lost primaries to challengers outside the House. Many of the toughest challenges to sitting members are still to come. Here's a look at four members facing difficult primaries over the next month:
Rep. Chuck Fleischmann (R-Tenn.) (August 2): The freshman Fleischmann has drawn two strong challengers in Weston Wamp, the son of ex-Rep. Zach Wamp, and Scottie Mayfield, the owner of Mayfield Dairy. They could end up splitting the anti-Fleischmann vote, but Fleischmann came into office via a close, crowded open GOP primary in 2010, and his 3rd District base might not be big enough in a smaller field.
Rep. John Conyers (D-Mich.) (August 7): A combination of age, ethics, and redistricting has led to a number of challengers filing to oppose Conyers in the 13th District -- only 35 percent of the district residents were represented by Conyers under the old congressional lines. A few candidates have gotten knocked off the ballot for filing too few petition signatures, but that may not help Conyers; he'll want the anti-incumbent vote split as many ways as possible to avoid defeat.
Rep. Paul Gosar (R-Ariz.) (August 28): Gosar is not even done with his first term, but he has already angered movement conservatives with some of his votes, including one for the debt ceiling compromise last year. Only one-third of the 4th District was in his old seat, and state Sen. Ron Gould has the support of the powerful Club for Growth. In his first ad, Gould blasted a copy of the health care reform law with a shotgun.
Rep. David Cicilline (D-R.I.) (September 11): Cicilline's overly rosy portrayal of Providence's finances has come back to bite him since he left the mayor's office and took over Rhode Island's 1st District in 2010. Cicilline has since apologized to constituents, but his ratings remain low and businessman Anthony Gemma is running partly on the idea that Cicilline is too weak to hold the liberal district against a strong GOP challenger in November.
Photo: House Judiciary Committee ranking member Rep. John Conyers, D-Mich, speaks on Capitol Hill in Washington, Tuesday, May 8, 2012. (AP Photo/Susan Walsh)