“This is to be a newscast of contextualization,” Mr. Olbermann told viewers on his new channel, Current TV. He promised to posit “that the weakest citizen in this country is more important than the strongest corporation.” His first guest and contributor was the muckraking filmmaker Michael Moore, who joined him in bemoaning President Obama's decision to not seek Congressional approval before attacking Libya. At the same time on MSNBC, Mr. Olbermann's successor, Lawrence O'Donnell, asked a longtime Obama confidant, David Axelrod, to respond to the president's critics on the issue of same-sex marriage.

Mr. Olbermann's new show looks the same as the old one, even down to the features, music and title, “Countdown With Keith Olbermann” but the pulpit is markedly different from his old perch at MSNBC. Current TV, a small, earnest network co-founded by Al Gore in 2005, favors civic-minded programs and averages about 50,000 viewers during prime time. Mr. Olbermann was wedged between two documentaries, “The OxyContin Express” and “Gateway to Heroin.”

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Mr. Olbermann, who quit MSNBC abruptly in January, is hoping that his new platform — politically progressive and free of corporate overlords, will attract left-of-liberal viewers seeking a more rabble-rousing champion. Mr. Olbermann assured his viewers that he and they would be the “last line of defense” against the “malfeasance of one political party and the timidity of the other.” He quoted Harriet Beecher Stowe on Abraham Lincoln and the Civil War. (“It is the war for the rights of the working classes of mankind, as against the usurpation of privileged aristocracies.”) He also noted, more bizarrely, that he is not the only person to start a new career on June 20 — Queen Victoria began her reign on the same day.

And his guests stoked his ego. Mr. Moore praised Mr. Olbermann for “keeping the good fight going.” Markos Moulitsas, founder and publisher of the liberal Web site Daily Kos, who is also a contributor to the show, called Mr. Olbermann a “national treasure.”

And it could well be that Current TV is better suited to Mr. Olbermann's personality than even his politics. Rachel Maddow and Mr. O'Donnell, the liberal commentators he brought to MSNBC and helped showcase, have developed their own followings, and Mr. O'Donnell has done respectably in his stead. Both anchors share Mr. Olbermann's righteous indignation, volubility and even his snarky sense of humor, but they come off as reasonable, respectable and even-keeled. ( Unlike Ed Schultz, the host of “The Ed Show,” who follows Ms. Maddow and seems like the cranky uncle who rants in post office lines — in May, Mr. Schultz was suspended from the network after calling the conservative firebrand Laura Ingraham a “right-wing slut” on his radio program.)

Mr. Olbermann, who has a colorful history of fighting with bosses and getting fired, is famously mercurial and thin-skinned. (Full disclosure: this critic was named “Worst Person in the World” at least once by Mr. Olbermann when he was on MSNBC.)

Even on the air, he looks as if at any minute he could lose his anchorman cool — a little like Jack Paar, who was famous for tearing up and sometimes walking out in the early days of the “The Tonight Show.” Mr. Olbermann's disputes with management were public and vociferous. He was suspended by MSNBC, a unit of NBC Universal, last November after giving money to three Democratic politicians. Current TV said that there is no problem there with political donations.

And he took every opportunity to bash corporate greed, summing up Monday's Supreme Court decision in favor of Wal-Mart this way: “The more employees you screw one way or the other, the more likely you are to get away with it, I guess.” John Dean, the former Watergate defendant, beamed at the host. “Nicely put,” he told Mr. Olbermann.

Viewers can be more fickle, as Conan O'Brien, now barely visible now that he is at TBS, can attest. But Mr. Olbermann tried to give his audience a stake in his survival by linking it to the fate of democracy. “Thank you for helping us preserve the freedom of the news,” he said.