Even in an age of old-media uncertainty, much is still made of the transfer of network anchor and host positions. Too often the discussion is purely about personality, but there’s more to it than a celebrity shuffle: the character and content of programs with rich histories and the potential for crucial contributions to civic discourse are at stake. So oceans of ink are spilled when CBS shifts the news anchor chair from Dan Rather to Bob Schieffer to Katie Couric; or when Tim Russert’s Meet the Press post goes to David Gregory. Unfortunately, scant attention has been paid to the coming shift of what over the past decade has become the most significant seat in broadcast journalism–the Friday night position occupied by Bill Moyers.

Moyers has been the most radical presence on broadcast and cable television since 2002, when the former White House press secretary, newspaper publisher, CBS and NBC commentator, bestselling author and award-winning documentarian settled into the work of producing weekly reviews not of the transitory arguments of the moment but of the great debates on the fate of the Republic. What has made Moyers, who will retire in April, such a radical presence is not his politics but his journalism.

As the host of NOW With Bill Moyers, Moyers on America and, since 2007, Bill Moyers Journal, he has provided an antidote to the blather served up by most news and public affairs programs. Never satisfied to practice stenography to power, as so many news programs do, or to moderate recitations of talking points by political hacks, Moyers refuses to treat Americans as imbeciles who need to be ideologically coddled.

Moyers has always chosen his guests with a purpose: to put new ideas, new analyses, new approaches on the table when most outlets invite talking-head insiders to narrow the range of options. So he has earned the ire of the political and corporate elites who benefit most from a constrained debate as he has cultivated an oasis for outliers who offer unbought and unbossed takes on wars of whim, executive excess, economic wrongdoing and, above all, the corruption of politics.

This has made Moyers, whose pronouncements in recent years have celebrated the populist and progressive reformers of a century ago, a tribune for some of the most insightful progressive thinkers of our time, including Barbara Ehrenreich, Lawrence Lessig, Glenn Greenwald, Michael Pollan, Nikki Giovanni, Roberto Lovato and George Soros.

But Moyers was never satisfied to push the ideological boundary to the left; he also pushed to the right. During the Bush/Cheney years, he hosted not only liberal and progressive critics of the administration (including editors and writers from this magazine) but also conservatives like Richard Viguerie, Cal Thomas and Ron Paul, the Texas Republican the host famously introduced, with a reference to Paul’s warnings about the folly of invading Iraq, as "a man who was right when no one listened."

Indeed, while other media outlets portrayed the mid-2000s as a time of simplistic partisan positioning, Moyers viewers were among the first to learn that true conservatives were angry with the GOP administration’s excessive spending and disregard for the Constitution. And then, after Barack Obama took office, Moyers began to highlight criticisms from the left and right of the Democratic president’s Wall Street-friendly economic policies and unfulfilled promises on torture and transparency.

This delight in dissent from conventional wisdom–from wherever it may come on the political spectrum–made Moyers a worthy successor to the late William F. Buckley, whose 1966-99 program, Firing Line, was similarly adventurous when it came to challenging compromised decision-makers and compromised journalism. A man of the mainstream right, Buckley invited onto his show libertarians and socialists, Margaret Thatcher and Jesse Jackson, Ronald Reagan and Noam Chomsky, Milton Friedman and John Kenneth Galbraith. Just as Firing Line mattered, not merely because of the topics but because of the liveliness and intelligence of the discussion, so watching Moyers has mattered.

The question is whether what comes next will matter. PBS plans to replace Bill Moyers Journal with a public affairs program featuring a new format. Whoever fills the slot will no doubt do things differently, which is to be expected. But it’s crucial that a forum be maintained for those with dissenting views–on the left and the right–and for those who are ready to toss aside talking points and wrestle honestly with the great issues of the day. Moyers has created a necessary forum, as did Buckley before him. To lose it would be disastrous, not just for PBS and broadcast television but for our Republic, which can ill afford the hollow hectoring and pointless positioning that passes for debate on TV programs that in entire seasons don’t say as much as Bill Moyers does in a single show.