Bernie Sanders. (Sean Rayford/Getty Images)

Bernie Sanders has been a mayor, a member of the U.S. House and, now, a senator. And yet, he lacks one thing that you would assume someone with that sort of resume would possess: a tuxedo.

"I do not own a tuxedo," Sanders told Time magazine over the weekend. "Never have I worn a tuxedo."

Stephen Colbert did a riff on Sanders's tuxedo-lessness on his Monday show, suggesting the likely reason was that "they don't make tuxedos in rumpled tweed."

Yes, it's funny. And, no, Sanders won't win or lose the Democratic presidential nomination based on whether he owns a tuxedo. But Sanders's lack of a tuxedo is, actually, quite telling -- and adds to the radical outsider vs. status quo insider dynamic that has helped the Vermont socialist make up ground against Hillary Clinton in this race.

Most people in America don't own a tuxedo. Many of them have never worn one either. (Confession: I do own a tuxedo.) Black-tie affairs are a regular happening in Washington, New York and Los Angeles. They are not a regular occurrence in most places in the United States.

As a result, tuxedos -- and the events people wear them to, such as the White House Correspondents Dinner -- tend to represent a sort of elitism that most people don't like. Those people in Washington, dressing up in their fancy outfits and celebrating one another when, in reality, they aren't doing much of anything for me, the argument goes -- or something like that.

That Sanders not only doesn't own a tuxedo but has never even worn one affirms the case he is trying to make to Democratic voters: I am in Washington, but I am not of Washington. I don't go to those dinners. In fact, I don't even get invited to them. I am the turd in the punchbowl -- and damn proud of it.

Implicit in that case for authenticity is the sense that Clinton is the epitome of Washington -- that she and her husband have attended hundreds of black-tie events in their long political careers. Clinton is the Washington establishment that Sanders has always ignored and, in turn, been shunned by.

It all gets back to a more-revealing-than-he-meant-it-to-be quote from Vice President Biden about the difference between Sanders and Clinton. Here's what he told CNN's Gloria Borger:

BIDEN: I think that -- that Bernie is speaking to a yearning that is deep and real, and he has credibility on it. And that is the absolute enormous concentration of wealth in a small group of people with the new class now being able to be shown being left out. There used to be a basic bargain. If you contributed to the profitability of an enterprise, you got to share in the profit. That's been broken. Productivity is up, wages are stagnant.

BORGER: But Hillary's talking about that, and ...

BIDEN: Well, it's -- but it's -- it's relatively new for Hillary to talk about that. Hillary's focus has been other things up to now, and that's been Bernie's -- no one questions Bernie's authenticity on those issues.

Sanders is the guy who has been fighting for liberal causes his whole life -- even when no one was paying attention and when he never imagined himself running for president. Clinton, in Biden's construction, has gone native on liberal causes because she knows that's what the moment requires. It's the difference between personal conviction and political positioning. And, in an election year like this one  -- where voters, Democrats and Republicans alike, want disruption -- it's a critical difference.

The tuxedo or, actually, the lack of one, is a powerful symbol that affirms that difference.

CORRECTION: This post initially said Sanders is a former governor. He was mayor of Burlington, Vt.