Rep. John Murtha, Democrat of Pennsylvania, passed away today.
Before this development, a pair of little-known Democrats were already challenging Murtha in the primary: Ryan Bucchianeri and Ron Mackell, Jr. On the Republican side, Tim Burns and Bill Russell were competing for the GOP nomination.
In 2008, Russell ran against Murtha and got 42 percent of the vote (polling earlier in the race showed him closer), holding Murtha to 58 percent. That was the smallest percentage for Murtha since 1974.
UPDATE: Chris Cillizza puts the special election on May 18.