Sen. Dick Clark, Rep. Bob Kreuger, Gov. Richard Lamm and Lt. Gov. Bob Rose are running for a variety of offices in a smattering of states.

All are Democrats; all are either ahead in the polls or running even against their opponents. Yet, more importantly, each has one more crucial thing in common: each faces the real possibility of losing in Tuesday's election, victim of one of the most increasingly influential blocs in American politics - the nonvoter.

Only 1 of every 3 persons eligible to vote Tuesday is expected to do so, as American voting turnout continues to slip as it has for almost two decades.

While low turnout can adversely affect both major parties, it hits primarily at Democrats, whose coalition of voting groups relies more on the lower-income and minorities who lack a strong voting tradition.

Indeed, polster Patrick Caddell has warned President Carter that "a very low turnout which is constructed such that Democratic groups turn out less than GOP groups could pose a significant threat to a number of our (Democratic) office holders."

So, he says, expectations for a good Democratic year may not be fulfilled and Republican gains "could well be greater than either predicted or merited by a turnout problem combined with some lesser factors."

Despite a broadening of the franchise - the voting age has been lowered, registration is easier poll taxes are gone - the number of nonvoters continues to rise faster than the number of people who vote. IN 1962, 45 percent of the eligible voters turned out in the off-year congressional election; in 1974, 36.1 percent did, and the one-third projection for Tuesday would about equal the turnout of the 1920s.

This shrinking turnout alarms many analysts who feel that elections will become arenas where narrow interest groups settle their differences over one issue.

"The real danger is not tomorrow, but it's getting to be tomorrow," says Curtis B. Gans, director of the Committee for the Study of the American Electorate. "Elections will be the adjudication between interest parties, people with an individual stake and the stake of us all."

Experts attribut the decline to a number of factors: a feeling there is no difference between candidates, a sense of powerlessness, a feeling that the vote doesn't affect things. Gans notes that after years of the Vietnam war, Watergate and other turmoils of government, "nothing has happened to turn that around" to restore confidence in the vote.

Perhaps reflecting that, it was a ballot initiative that turned out voters in California, Proposition 13, and similar tax-cutting referends in 17 other states are expected to excite voters more than candidates. On these issues, there is a choice - year or no - that does not appear to many voters when they watch talk alike candidates.

The toll that low voter turnout exacts on Democrats is reflected in places like south Texas, where they have been pushing hare recently to build enthusiasm among Mexican-American voters. Democratic Senate candidate Krueger, who is challenging Republican incumbent John Tower, has made strong gains among Hispanics in Texas. He has the endorsement of their leaders, the Hispanic Caucus from the state legislature is stumping the state - but whether the votes will materialize on Tuesday is still unknown.

Similarly, State Rep. Mickey Leland, an upopposed black Democrat who will succeed retiring Rep. Barbara Jordan (D-Tex.), has been touring black areas in places like west Texas and in Houston, urging minorities to vote or face the prospect of a Republican governor.

On paper, the Republican candidacy of Bill Clements, former deputy secretary of defense, is a laugh. He has produced such headlines as, "The ERA: Clement Clarifies His Stand on It for Third Time."

He also had to apologize to the mayor of Amarillo after, in some bizarre political gesture, he threw a rubber chicken at her and it landed in her dinner plate. Clements, an oil drilling contractor who says his net worth is $29.4 million, is spending perpahps as much as $10 million, most of it his own money. This combined with a Republican core, some crossover Democrats, and low Democratic turnout, by some scenarios, could put him in the governor's office.

Currently, however, a nonpartisan statewide poll conducted for Texas Monthly magazine gives Democrat Attorney General John Hill a solid lead, with much of that support coming from blacks and Mexican Americans. Kruegar holds a narrow a lead in that poll.

Not surprisingly, the Democratic National Committee, as part of a nationwide campaign, is running radio commercials in Texas urging Democrats to go to the polls on Tuesday.

Clark of Iowa, seeking reelection for the Senate, Lamm, who is up for reelecation in Colorado, and Rose, campaigning for governor of Nevada, similarly show leads or dead heats with their opponents in the polls. But among those polls of likely voter, they either run second or see their support reduced.

Significantly, there are all Democrats who appear to be affected by low turnout. In the low turnout year of 1974 it was large numbers of Republicans who stayed at home, giving the Democrats stunning gains in the Congress that remain today.

Whatever the impact on individual candidates, not everyone agrees that lower vote turnout is necessarily a bad thing.

Election analyst Richard Scammon, for one, cites Switzerland as having a low voter turnout and "government that works very well, thank you," and also notes that Italians have high voter turnout and unstable government.