Nonetheless, Gergen is on to something. Obama did something unusual for a president: By going on Galifianakis’s show, he put himself in a situation where his office did not insulate him from potential ridicule. To survive, he had to rely on his wits. And that’s precisely why it proved such an effective move.

Since the days of Eisenhower and JFK, the relationship between presidents and the public has changed profoundly. In 1964, according to the Pew Research Center, almost 80 percent of Americans trusted government to do the right thing “most of the time.” By 2013, it was 19 percent.

If you look at the data, you can sense what’s happened. To simplify, the decline starts in the late 1960s, when Americans learned that their leaders had lied about the disastrous war in Vietnam, and continues through the Watergate scandal and the economic stagnation of the 1970s. Public faith rebounds somewhat during the economic boom of the late 1990s and after September 11 before plummeting again in response to another disastrous and dishonestly justified war and a financial implosion that has caused widespread economic pain.

The key point is this: While recent presidents may have adequately “protected the majesty of their office” when it comes to edgy comedy shows, they haven’t adequately protected it when it comes to sending America’s soldiers to their death or protecting against massive, job-wrecking financial fraud. For this (and probably other) reasons, today’s presidents cannot simply assume—in the ways Truman, Ike or JFK could—that Americans will believe them, respect them or even listen to them, merely because of the office they hold.

Indeed, some of the most successful comics of the post-9/11 age have spent their time sabotaging the claim that America’s leaders deserve the deference traditionally accorded them. Think of Stephen Colbert’s running gag “Better Know a District,” in which he makes members of Congress look stupid, or at least stiff. Or Ali G’s ambush-interviews of politicians and other big wigs. Here’s Ali G interviewing Newt Gingrich in 2003:

Although more raunchy, the interview is a lot like Galifianakis’s with Obama. In both, the comics instantly undermine their subject’s authority by pretending to be unfamiliar with their names. The difference is that because Obama’s in on the gag, he doesn’t come across as pompous. Instead, he comes across as funny, smart, and self-aware—all of which, ironically, gives him the authority to sell Obamacare to an audience that doesn’t see being president itself as authority enough.

By refusing to defer to the office of the presidency, Galifianakis allowed Obama to remind his supporters of what they like about him. To Obama’s admirers, he represents American meritocracy at work. Unlike many leading politicians, he was raised with no special advantages. To the contrary, he succeeded—despite an absent father, an exotic name, and black skin—because of his intelligence, eloquence, and ability to adapt to environments as diverse as Chicago housing projects, Harvard Law School, and the presidential-campaign trail. By putting Obama in an unfamiliar and unpredictable environment, where he was forced to rely on his wits alone, Galifianakis helped Obama display his signature talents. It’s no coincidence that Galifianakis ended the interview with a dig at George W. Bush, whose advisers would never have risked such an unscripted exchange. (Here’s Jon Stewart begging Bush, unsuccessfully, to come on his show during W.’s post-presidential book tour).