In one way, Jonathan Martin's story about the plagiarized Army War College thesis of Montana Sen. John Walsh broke at just the right time. The New York Times reporter revealed Walsh's plagiarism on July 23. That was after Walsh won a primary, dispatching two opponents who ran to his left, but before Aug. 11, when the state party could replace any candidate who left a race.

And that was what Walsh eventually did. Today he quit a race that he'd always been expected to lose—one that he'd started to gain a little ground in, before his past exploded in his face—after informing his campaign staff. "I am ending my campaign so that I can focus on fulfilling the responsibility entrusted to me as your U.S. senator," he said in a statement. "I am proud that with your support, we held our opponent (Daines) accountable for his hurtful record to privatize Medicare to deny women the freedom to make their own health decisions and to sell off our public lands." Yes, even in defeat, he stayed with the DSCC's preferred message.

Montana Democrats now have a chance to assemble, and for less than 200 delegates to pick a new candidate. Missouri Republicans tried to pull something like this off in 2012, when Rep. Todd Akin blurted "legitimate rape" with some time left for the party to pick a new candidate. The difference: In 2012, Republicans figured (not incorrectly) that any warm body with an "R" next to it on the ballot could beat Claire McCaskill. Montana Democrats are trying to hold an open seat in a state that has not voted Democratic for president since 1992. They have an unusually good record of winning Senate races in the state, but not under these red-alert conditions.