President Obama made his final appearance on "The Daily Show" with Jon Stewart as host. Here's a look back at some of the president’s most notable moments on the show. (Emily Rhyne/The Washington Post)

When I appeared on “The Daily Show” in late 2002, host Jon Stewart wanted to know why conservatives seemed to have a more effective message than progressives. “Are they better at selling their ideas, or they just have better ideas?” he asked. Although I disputed his premise, the Bush administration and its allies clearly had marginalized progressive opposition to the impending war in Iraq, and Stewart still thought of himself as an impartial observer. “Join us in the center,” he said as the interview concluded. “That’s my movement.”

But it wouldn’t be long before Stewart, whose 16-year run on “The Daily Show” comes to an end next week, became one of the most important and influential voices on the progressive left — an improbable icon who cut through right-wing talking points with satire while making progressive ideas sound like common sense. Stewart’s show provided valuable airtime to views that were often neglected, even denigrated, in mainstream media, and made them sound appealing. And by reviving political humor on a nightly basis, he helped turn on young (and old) people to politics and broaden the progressive base.

The U.S. invasion of Iraq was a turning point in Stewart’s career. While most of the media cheered on the war and caricatured its opponents, Stewart transformed “The Daily Show” from simply “fake news” into something far more significant: a place for dissent. As media critic David Folkenflik wrote in April 2003, “For those who like to see television take antiwar figures seriously — or at least somewhat seriously — there’s really been only one sure place to turn in recent weeks: Comedy Central’s ‘The Daily Show.’ ”

Stewart mocked the media’s coverage of the invasion by, for example, replacing the triumphant soundtrack behind Fox News’s bombing footage with “tacky 1970s-style funk.” But he also found his voice and used it to push back against a dominant political and media establishment that gave little credence to progressive opposition to the war. “It’s as though there’s only two positions you can have,” he observed. “You’re either for the war or against the troops.”

As the years passed, Stewart continued to question the logic behind the Iraq war and, indeed, the entire “war on terror,” perhaps most notably in his 2008 interview with former British prime minister Tony Blair. “19 people flew into the towers,” Stewart said to Blair, a strong supporter of the Bush administration’s strategy. “It seems hard for me to imagine that we could go to war enough, to make the world safe enough, that 19 people wouldn’t want to do harm to us. So it seems like we have to rethink a strategy that is less military-based.”

Stewart’s contribution to the public debate was not limited to the realm of foreign policy. In April 2009, he hosted Elizabeth Warren, then a little-known Harvard Law School professor appointed by Congress to provide oversight of the Troubled Asset Relief Program (TARP). During the interview, Warren explained that “pulling the threads out of our regulatory fabric” had led to the financial crisis and made a clear argument for stricter regulations on big banks. “That was like financial chicken soup for me,” Stewart responded. “That actually put things in perspective and made a little sense.” As Warren rose in prominence and became a progressive stalwart in the Senate, her political career was fueled in part by regular appearances on “The Daily Show,” where she was a guest six times.

While Stewart elevated progressive voices and ideas, he also was a vocal and relentless media critic. As the coverage of politics grew more trivial, polarizing and less informative, Stewart pleaded for a better discourse, famously castigating the hosts of CNN’s “Crossfire” for, in his words, “hurting America.” And perhaps nobody on television did more than Stewart to define Fox News as the reliably partisan outlet that most people know it as today.

Perhaps the most remarkable thing about Stewart, however, is the vast influence he commanded from his perch on late-night cable. For a generation of Americans, Stewart provided a political education that helped shape their worldview. Indeed, as early as 2004, there was evidence that young people were increasingly getting their information from “The Daily Show” instead of more traditional sources. And for the past decade, public surveys have consistently rated Stewart among the most popular and trusted names in news. Although it’s impossible to prove, Stewart is almost certainly one of the reasons that younger Americans are so progressive.

“What’s important is doing something worthwhile,” Stewart said in 1998 before he took the reins at “The Daily Show.” Judging him by that standard, Stewart’s tenure has been an astounding success. He made us laugh, yes, but he also encouraged us to think. He challenged the conventional wisdom and amplified dissent. He was a small-d democrat in the truest sense of the word, always holding the powerful to account for putting the public interest behind their own. That’s his legacy — and nothing could be more worthwhile.

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