This has got to be the most transparently contrived "feud" between two politicians of the same party that I've ever seen. It's Mark Begich (D-AK), running for re-election in a tight race that could tip the balance in the Senate, taking on Claire McCaskill (D-MO), whose own re-election in 2012 was fraught until the GOP nominated Todd Akin. After letting Begich knock her around for a few days on an issue of great importance to Alaskans, McCaskill really "retaliated" today in a statement to TPM: "There has consistently been one problem—Mark Begich. He single-handedly protects Alaska and the ANCs.”
Dylan Scott explains the whole thing.