Keith Olbermann has departed MSNBC, anchoring his last “Countdown” on the news network this evening.

“MSNBC and Keith Olbermann have ended their contract,” the network said in an announcement on Friday, but did not elaborate on a reason. Near the end of his show, Olbermann announced that his appearance would be his last.

Olbermann, one of the network’s signature stars, was briefly suspended in November after it was disclosed that he had contributed to several candidates in violation of network policy.

“MSNBC thanks Keith for his integral role in MSNBC’s success and we wish him well in his future endeavors,” the network said in a statement.

Lawrence O’Donnell’s show, currently called “The Last Word,” will move to 8 p.m., while “The Ed Show” will move to 10 p.m. Cenk Uygur, a contributor to MSNBC and host of the web show “The Young Turks,” will fill in as host of the 6 p.m. hour, the network said.

Brian Lowry writes that the timing, just days after Comcast received government approval to take control of NBC Universal, is sure to rause eyebrows.

“Last May, Comcast CEO Brian Roberts was asked about whether he was ready for the headaches associated with running NBC U during an interview at the Cable Show. Former News Corp. COO Peter Chernin specifically wondered what Comcast would do if an MSNBC host created a stir that threatened the company’s larger interests.

“Roberts sidestepped the question, but did say regarding NBC News, “The single most awesome asset that comes from this deal is NBC News. … NBC News will help define Comcast.””

On his final show, Olbermann did not go into details of what led to his departure, but did reference the movie “Network,” in which the provocative anchor of a nightly news show is assassinated on the air by his own network when he becomes too outspoken.

“I think the same fantasy has popped into the head of everybody in my business who has ever been told what I have been told, that this is going to be the last edition of your show,” Olbermann said. “You go directly to the scene from the movie ‘Network,’ complete with the pajamas, and the raincoat, and you go off on an existential, otherworldly journey of profundity and vision. You damn the impediments and insist upon the insurrections, and then you admit Peter Finch’s gutteral, resonant, Soooo. And you implore, you will the viewer to go to the window, open it, stick out his head and yell…well, you know the rest.”

“Your support and loyalty ultimately required that I keep going,” he said to viewers, whom he thanked along with his staff. He called Tim Russert “my greatest protector and the most indefatigable cheerleader.”

Here is what Olbermann said on the show this evening.

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