Washington ? Is it a way to improve the nation’s political discourse? A way to tip some votes just before the election? Or just a big outdoor comedy show?

Organizers insist that Jon Stewart and Stephen Colbert’s “Rally to Restore Sanity and/or Fear” on the National Mall today isn’t about politics. But that hasn’t dampened the expectations of thousands of fans and advocacy groups seeking to rekindle some of the voter enthusiasm seen in 2008, particularly among young adults.

For many of them, that civic engagement would translate to a boost for Democrats — a calculation President Barack Obama bet on this week when he became the first sitting president to appear on Stewart’s “The Daily Show” on TV’s Comedy Central. Obama said his message was still “Yes, we can” — “but it’s not going to happen overnight.”

“This rally is attracting a lot of attention, and it could have an impact because the target demographic of young people who tend to vote Democratic needs more mobilization to vote than do older people,” said Scott Keeter, director of survey research at the nonpartisan Pew Research Center.

A Pew poll last month found 41 percent of Stewart’s fans identify themselves as Democrats, compared with 38 percent independents and 14 percent Republicans. His audience also tends to be younger than for many other cable programs, a key segment since adults 18-29 are half as likely than those 30 and older to vote.

“Any shift in a Democratic or Republican direction coming from a change in the national mood, from whatever outside force, could tip a lot of races because they seem to be so balanced on a razor’s edge at this point,” Keeter said.

A preliminary list of entertainers includes musicians Sheryl Crow and The Roots. Actor Sam Waterston and Don Novello, who played Father Guido Sarducci on “Saturday Night Live,” are also expected to appear.

The event is described on its website as a place for people who want to see a return to sanity — those who think “shouting is annoying, counterproductive and terrible for your throat, who feel that the loudest voices shouldn’t be the only ones that get heard, and who believe that the only time it’s appropriate to draw a Hitler mustache on someone is when that person is actually Hitler.”

Organizing for America, Obama’s political operation based at Democratic National Committee headquarters, is setting up a “Phone Bank for Sanity” after the rally to urge people to vote on Tuesday.