When David Letterman left "Late Show," he went straight to the Indianapolis 500, where his team Rahal Letterman Lanigan was racing.

When Johnny Carson left "Tonight," he went to his beloved tennis court in Malibu.

When Jay Leno left "Tonight," he went back out on his beloved stand-up circuit.

When Jon Stewart leaves "The Daily Show," he will . . . WHAT?

Stewart ends his celebrated 16-year "Daily Show" run Thursday night. But what exactly are celebrated late-night hosts supposed to when the gig is up? What exactly will Stewart do?

At 52, he's too old to pursue a new career -- let's blue-sky it here -- as a concert pianist or cardiologist. He's also too young to retire. The possibilities, therefore, are alluring and extensive. Or are they?

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Let's parse:

POLITICAL OFFICE

I place this idea at the top to dispense with it quickly. How many times must Stewart emphatically say "no" to this idea -- as he so often before has when it is broached -- before people actually believe him? "People," in this instance, tend to be fans who view him as the avatar of liberal causes -- a natural-born politician who could bring real change to Washington and the world. But that is wishful or shallow thinking. Stewart is not a natural-born politician with a taste or talent for the crucial retail side of the trade, which involves getting votes, twisting arms, trolling for support on a beloved bill, or gutting a despised one. He's a comedian with a rapier wit who does not suffer fools. Politicians -- as a condition for getting anything done -- must sometimes suffer them gladly.

DIRECTING MOVIES

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This looks appealing from afar, but the focus blurs a bit upon closer inspection. His 2014 indie release "Rosewater" got respectful reviews, but "respectful" is a long way from "ecstatic." Hollywood and New York are filled with gifted directors, some supremely gifted ones, all of whom scrap hard for desirable projects. Like politics, it can involve some knife-throwing, too. Does Stewart have the stomach and talent for this? Only he knows the answer for certain.

BACK TO STANDUP

Jerry Seinfeld did it; why not Stewart (who did a set at the Comedy Cellar a couple of weeks ago)? I tend to think, however, Stewart sees the standup road as an even harder grind than the nightly TV one; plus it takes him away from his family for long stretches. One thing he has made perfectly clear: He wants a lot more family-time. Nevertheless, there's nothing wrong with the occasional standup gig to keep the tools sharpened.

A WEEKLY SHOW

Ah yes, the prestige vehicle on HBO or Showtime, maybe like "Last Week Tonight with John Oliver," or something no one has even thought of? The appeal here is possibly twofold: 1) He could polish something to a high gloss, unencumbered by daily deadlines. 2) He wouldn't even have to star on the show. This last point just might be the clincher because Stewart has long said that he no longer wishes to be on TV on a regular basis, if at all.

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'NIGHTLY SHOW WITH LARRY WILMORE'

I leave this to last because it is indeed the most immediate challenge, possibly the most urgent, too. Stewart's Busboy Productions remains the producer in charge of "Nightly," while Stewart himself is an executive producer. As such, he already has a post-"Daily Show" job, which everyone seems to have overlooked. There's work to be done: As host, Wilmore is good, but his numbers are poor (around 800,000 viewers in late July). Behind the scenes, Stewart can now give his full creative attention to this, while still developing other projects or shows. This seems to me the most likely post-"Daily Show" move at the moment.