As Campaign '80 enters its final weeks, none of the three presidential candidates has yet found the magic formula needed to mobilize the tens of millions of young adults in America's baby-boom generation who have never voted, nor in many cases even bothered to register.

And what there is of the youth vote -- normally a Democratic preserve -- is being skewed much more than the older vote by the wild-card candidacy of independent John Anderson.

These not-surprising conclusions drawn from a Washington Post poll taken earlier this month and from other recent surveys.

Young Americans this year have been wooed passionately, and expensively, by politicians who view them as a potentially key voting bloc. And with the Carter-Reagan match shaping up as a dead heat, an influx of new voters from any quarter becomes especially important.

But only 62 percent of those age 35 and younger said they had registered as of Sept. 7, compared with 86 percent of those 36 and older, according to the Post poll. Pollsters normally allow for a "lie factor" of 6 percent, which would put the figure at 56 percent who really have registered. By rough estimate, then, nearly 30 million young adults 35 and under have not registered.

Of all young adults 35 and under, fully a quarter not only have not registered but say flatly that they have no intention of doing so.

The rate of registration among the young is virtually unchanged from this same point in 1976, according to a recent Gallup poll. Gallup notes also that only eight out of ten of those registered to vote actually will cast a ballot, if they follow past voting patterns.

The younger the age group, the higher their rate of abstention from the electoral process.Just over half of the 18-to-29-year-olds say they have registered, while over three-fourths of the 30-to-35-year-olds say they have, according to the Post poll.

Traditionally, people start to vote as they grow older and "settle down." But an earlier Post poll indicated that that has not yet happened in this generation. Virtually the same percentage (32.5) in the 27-to-35 age group said they did not vote in 1976 as in the 18-to-26 age group (32.6).

Among young adults, much more than among older people, education makes a difference in attitudes toward voting. Among the 35 and under population, only 45 percent of those with less than a high school education said they have registered to vote. By contrast, 78 percent of young adults with college educations or better say they are registered.

People 36 and older tend to be registered no matter what their level of education. For example, 81 percent of those with less than a high school education say they are registered.

Robert Teeter, an influential pollster for the Republicans, predicted earlier in this campaign that these alienated potential voters "are not going to go through their entire lives not participating in the process," and speculated that the 1980 election could lure them to cast their ballots in significant numbers.

To help them into the GOP column, the Republicans launched an unprecedented $8.5 million television ad campaign aimed at these eligible young voters, particularly high-school educated blue-collar workers who earn $18,000 to $20,000 a year.

This week, Teeter said his surveys show "no evidence that anybody will bring great new waves of voters to the polls."

But he added, "The [TV] ads aren't designed to increase turnout, but to bring about attitudinal change." His surveys showed that public attitudes toward Republican candidates have improved, he said.

Reagan, meanwhile, was having more luck in getting blue-collar Democrats to switch, Teeter said, than in bringing in new voters. He said that Reagan also continues to get a vital boost from the Anderson candidacy.

Anong young adults who say they are registered to vote, Reagan leads with 38 percent to Carter's 32 and Andersons's 17, the Post poll found. Carter leads Reagan among those who say they don't plan to vote.

A poll by Lou Harris conducted at the same and focusing on "likely voters," showed similar results with slightly different age breakdowns. Reagan either led or ran even with Carter.

But when Anderson's name was dropped, Carter picked up 18 points, while Reagan only picked up 8, with a 54-to-44 Carter lead blossoming among 18-to-29-year-olds who are likely to vote.

In other age categories, Carter's gains were significantly smaller.

The continuing low level of participation among younger people is part of a two-decade decline in voter participation in this country, a decline often attributed in large measure to cynicism and alienation caused by such events as the Vietnam war and Watergate.

But what distinguishes voters from nonvoters primarily -- at least as measured in recent polls -- is how they feel about the two major political parties. Nonvoters believed in much greater proportions that it makes no difference whether Republicans or Democrats win.

"Anderson is the joker" in this election deck who could increase, or at least halt the downward trend in voter participation this year, according to Curtis Gans, director of the Committee for the Study of the American Electorate.

"If [at the time of the election] Anderson shows up as viable, with 15 to 30 percent support, then voter turnout will increase," he said, because those discontented with the system will have a place to hang their hats.

Meanwhile, the first real baby-boom candidate remains undetected in the wings somewhere.

"This has been a difficult group for any candidate to communicate with," Teeter said, adding that most politicians tend to stereotype the crucial blue-collar vote as balding, 55-year-olds who served in World War II. "They are more likely to be 24 years old, wear a rag around their head and drive a van to work. I don't see anybody coming along who has the soul of that generation."