For the past few years, television has offered a popular situation comedy built around idealistic '60s parents trying to fathom their pragmatic '80s children. Now comes the Democratic Party, delving into the same mystery but with a mission to find votes, not laughs.

The House Democratic Caucus is dispatching 50 of its younger members to colleges across the country this week on a political sales trip that begins with the question: How come you kids aren't good Democrats?

"The catalyst was the last election," Rep. Richard J. Durbin (D-Ill.), who conceived of the campus program, said. "We'd been taking the youth vote for granted so long that we lost it."

According to NBC exit polls last year, President Reagan carried 18- to 24-year-old voters by 59 to 41 percent, the same ratio by which he won the election. It was the first time since adoption of the constitutional amendment allowing 18-year-olds to vote that this group did not vote more Democratic than the rest of the electorate.

Durbin believes this falloff is largely a product of a "cult of personality" around the president, and that as the Reagan era passes, Democrats can recapture the youth vote by serving up some well-crafted reminders of the values and compassion their party identifies with.

But if a kickoff forum at Georgetown University late last week was any guide, the task at hand may be a bit more daunting than Durbin or his colleagues anticipate.

The Democrats sent seven of their most attractive young voices to the university's ornate Gaston Hall: Reps. Richard A. Gephardt (Mo.), Tony Coelho (Calif.), Mickey Leland (Tex.), Mary Rose Oakar (Ohio), Mel Levine (Calif.), Marcy Kaptur (Ohio) and Durbin.

Each spoke for about 10 minutes, describing how their experiences had drawn them to public service -- as Democrats.

Coelho told of his despair as a young man upon learning that he was epileptic, and having some of life's doors closed to him. He also reminisced about cutting college classes to watch President Kennedy's televised news conferences. "They were thrilling," he said.

Kaptur talked of what it meant to be the first member of her family to attend college, on government loans.

Leland told of his student days as a civil rights and antiwar activist; of what it meant to grow up poor and fatherless; of never sitting in a classroom with a white child; of his pride at being one of 52 blacks to have served in Congress.

Levine talked of touring Central America as a college student and seeing two objects in every mud hut -- a crucifix and a picture of John F. Kennedy.

These were '60s kids, now grown, remembering what it was like to be young. Their audience of 150 listened attentively.

Then came the questions.

"How come," a junior led off, "the Democratic Party is so disorganized?" She told of stuffing envelopes as a volunteer for a Democratic campaign and becoming distressed by all the duplicate addresses. "It seems like a lot of Democrats are proud of the image of being disorganized," she said.

"You told us what your party has done for blacks, women and the disabled," chimed in another audience member, Tony Byergo of Kansas City, who, like the first questioner, identified himself as a Democrat. "You told us about civil rights and about President Kennedy. What you haven't told us is what you've done for us lately."

The let's-get-down-to-cases quality of the questions went straight to the generational chasms in the room.

The panelists had grown up in a period when, whatever else was going on, economic opportunity seemed boundless. There was plenty of time for causes.

The audience had grown up in an era of economic uncertainty. Today's young people seem to want to get every last drop out of today, and still have something left over to guard against tomorrow.

In 1984, according to a national survey by Alexander Astin of the University of California at Los Angeles, 71 percent of college freshmen said that "being very well off financially" was a very important goal, up from 39 percent in 1970.

The panelists tried to adapt their remarks to their demanding audience. They talked about how the trillion dollars added to the national debt under Reagan has every American $15,000 in the red. They talked about how trade deficits are costing jobs, how $600 Pentagon toilet seats are burning tax money. They said the Democrats would do better.

It was a good political pitch -- but merely that. It had none of the fire of Democrats' tales of yore. The audience, polite throughout, began to drift away.

"We don't anticipate any great epiphanies to emerge from this forum," Durbin had cautioned at the outset.

If there were any to be had that night, one suspects they flowed from the audience, not to it.