Keith Olbermann has been fired by Current TV, the network announced Friday. He will be replaced by former New York governor and CNN host Eliot Spitzer.

Spitzer, who had his own short-lived stint as the host of "Parker Spitzer" (later called "In The Arena") on CNN, began hosting his show, "Viewpoints," immediately on Friday night. He made no mention of Olbermann or his somewhat unusual arrival to the post at the top of the show.

The news of Olbermann's termination was first reported by the New York Times' Brian Stelter.

A source told Politico that Olbermann was fired for breach of contract, saying that he had "sabotaged" the network. Howard Kurtz reported that Olbermann had begun refusing to toss to other peoples' shows or appear in advertisements with them.

Another source told the New York Observer that Spitzer had been in talks with Current for months.

The channel released a statement signed by Al Gore and Joel Hyatt, the founders of the network, on Friday. The statement made plain that Current's relationship with Olbermann had devolved to an unsustainable point:

To the Viewers of Current: We created Current to give voice to those Americans who refuse to rely on corporate-controlled media and are seeking an authentic progressive outlet. We are more committed to those goals today than ever before. Current was also founded on the values of respect, openness, collegiality, and loyalty to our viewers. Unfortunately these values are no longer reflected in our relationship with Keith Olbermann and we have ended it.

The statement also called Spitzer "an astute observer of the issues of the day."

Olbermann also released a statement in 140-character chunks on Twitter, saying that he would be taking legal action:

I'd like to apologize to my viewers and my staff for the failure of Current TV. Editorially, Countdown had never been better. But for more than a year I have been imploring Al Gore and Joel Hyatt to resolve our issues internally, while I've been not publicizing my complaints, and keeping the show alive for the sake of its loyal viewers and even more loyal staff. Nevertheless, Mr. Gore and Mr. Hyatt, instead of abiding by their promises and obligations and investing in a quality news program, finally thought it was more economical to try to get out of my contract. It goes almost without saying that the claims against me in Current's statement are untrue and will be proved so in the legal actions I will be filing against them presently. To understand Mr. Hyatt’s “values of respect, openness, collegiality and loyalty,” I encourage you to read of a previous occasion Mr. Hyatt found himself in court for having unjustly fired an employee. That employee’s name was Clarence B. Cain. In due course, the truth of the ethics of Mr. Gore and Mr. Hyatt will come out. For now, it is important only to again acknowledge that joining them was a sincere and well-intentioned gesture on my part, but in retrospect a foolish one. That lack of judgment is mine and mine alone, and I apologize again for it.

Olbermann's lawyer, Patricia Glaser, told Deadline he would be suing. "[Current] can expect a bad a result," she said.

It was also announced Friday that Olbermann will appear on David Letterman's show on Tuesday to discuss his departure.

Olbermann's firing leaves what was supposed to be his triumphant return to television in tatters. After his bitter departure from MSNBC, Current sought to make him the centerpiece of its rebranding as a progressive news network. It granted him the title of Chief News Officer, gave him an equity stake in the company, and promised that his uncompromising brand of television would be the cornerstone of its programming. Announcing the beginning of the partnership, Al Gore said that he was "extremely honored and delighted" that Olbermann was joining him, and called it "a great fit in every way."

It was not long, though, before the tensions between Olbermann and his superiors exploded into the open. In January, his sudden absence from Current's coverage of the Iowa caucuses led to open warfare between the two sides. Olbermann fired off a statement saying that he was “not given a legitimate opportunity to host under acceptable conditions,” adding, “They know it and we know it. Telling half the story is wrong.”

There were also reports that Olbermann was incensed by repeated technical problems with his show, and miffed that he was not being given a greater say in deciding which shows were going to precede and follow his. (During his time on Current, the network added shows featuring Cenk Uygur at 7 PM and Jennifer Granholm at 9 PM.)

Olbermann, often citing medical issues, also began missing some days of work, something that apparently was used against him in his firing. One of the people who had filled in for him, ironically, was Eliot Spitzer.

As one executive said rather presciently during the height of Olbermann's conflicts with the network, "Everybody is replaceable."