Keith Olbermann announced during the telecast of tonight's episode of "Countdown with Keith Olbermann" that this would be his last show after an 8-year run on MSNBC.

As the show aired, MSNBC put out this statement: 

"MSNBC and Keith Olbermann have ended their contract. The last broadcast of 'Countdown with Keith Olbermann' will be this evening. MSNBC thanks Keith for his integral role in MSNBC's success and we wish him well in his future endeavors."

MSNBC also announced that "The Last Word with Lawrence O'Donnell" would be taking over the 8 p.m. timeslot starting Monday, with Ed Schultz's "The Ed Show" replacing "The Last Word" at 10. "Rachel Maddow" will remain at 9 p.m.

This is the second time Olbermann has left MSNBC. In 1998, he left in frustration after his primetime show became largely devoted to covering the Monica Lewinsky scandal. He returned in 2003, initially as a fill-in for Jerry Nachman.