For nearly a year now, Al Gore and Joel Hyatt have been building their liberal cable news channel, Current TV, with the mercurial television anchorman Keith Olbermann at its center.

This week, the center collapsed.

Current said Friday afternoon that it had fired Olbermann — one of the nation’s most prominent progressive speakers — just a year into his five-year, $50 million contract.

It was the culmination of months of murky disputes between Olbermann and the channel that he was supposed to save from the throes of ratings oblivion.

Yet as inevitable as it might have seemed to some in the television business who know the long history of antipathy between Olbermann and his employers, it was nonetheless shocking to his fans, to his detractors, and to staff members at Current when the announcement was made.

Forty-five minutes afterward, in a stream of Twitter messages, Olbermann threatened to take legal action against the channel and said its claims about him were untrue. In part because of the prospect of litigation, executives at Current declined to comment on the firing Friday. But they immediately named as his replacement Eliot Spitzer, the former governor of New York, who took over Olbermann’s 8 p.m. time slot Friday. It represents Spitzer’s second shot at an 8 p.m. talk show; in 2010, two years after he resigned the governorship after he admitted having patronized a prostitution ring, he co-led a short-lived show on CNN. It was canceled in mid-2011.

In a letter posted on Current’s website, Gore and Hyatt wrote, “We are confident that our viewers will be able to count on Governor Spitzer to deliver critical information on a daily basis.”

With those words — “on a daily basis” — the founders of Current hinted at one of the reasons for Olbermann’s termination.

He clashed early and often with Hyatt, and especially with David Bohrman, a former CNN executive who was installed as president of Current last summer. The clashes became visible when Olbermann started anchoring his program, “Countdown,” in front of a funereal black backdrop, apparently out of frustration about technical difficulties. He also declined Current’s requests to host special hours of primary election coverage in January, causing lawyers from both sides to intercede. Eventually an election coverage plan was cobbled together, but in January and February, Olbermann continued to miss many days of work, as he himself acknowledged on his Twitter page. He attributed some of his absences to throat problems.

In public, Current remained supportive of Olbermann, whom Hyatt called “the big gun in our lineup” during an interview March 5 to promote new political programming on weekday mornings.

“It’s all on top of his shoulders,” Hyatt said, even as he added new programs, in part as a hedge against the possibility of Olbermann’s departure.

In a termination letter Thursday morning, Current cited “unauthorized absences” as one of the reasons. It also cited a failure to promote the channel and disparagement of the channel’s executives.