Explaining why he didn't vote in the 1978 congressional elections, a 27-year-old oil field machinery repairman in a small town in southwest Texas said, "I didn't feel any of the candidates were qualified." From what he says, he probably won't vote this year either.

A 44-year-old woman who works in a factory in northern New Jersey also is unlikely to vote in November. In 1978, she said, "I wasn't interested in any of the candidates. They weren't helping poor people, they were helping the rich."

Another probable nonvoter is a young woman doctor from suburban Detroit who did not vote in the 1978 congressional or 1980 presidential elections. Her first inclination is to blame herself, saying, "Apathy, I suppose."

But apathy is only part of the story. For the great majority of citizens interviewed in a nationwide Washington Post-ABC News poll, anger at Congress and frustration with the two political parties are important factors in the the growing phenomenon of nonvoting in the United States.

The nationwide decline in voting has been particularly steep in recent years, especially when, as this year, there is no presidential election. In 1970, 43.5 percent of eligible voters turned out for congressional races across the country. In 1974, after the Watergate scandal, the turnout fell to 36.2 percent, and in 1978 it was down to 35.5.

Political observers are predicting that turnout will be even worse on Nov. 2. The Post-ABC News poll, conducted from Sept. 9 to Sept. 13, suggests they are correct.

"I just felt the candidates were not ones who I'd be interested in," explained the Detroit doctor when pressed about why she did not vote in 1978.

The great majority of Americans agree with her, according to the poll, which shows most nonvoters -- as well as voters -- hold Congress in deep contempt.

This is reflected in responses to these questions from the poll, in the form of statements answered by "agree," "disagree," or "no opinion."

Q. "To win elections, most candidates for Congress will make campaign promises they have no intention of fulfilling."

A. Agree, 72 percent; disagree, 22 percent; no opinion, 6 percent.

Q. "Most members of Congress care deeply about the problems of ordinary citizens."

A. Agree, 40 percent; disagree, 53 percent; no opinion, 7 percent.

Q. "Most members of Congress will tell lies if they feel the truth will hurt them politically."

A. Agree, 73 percent; disagree, 19 percent; no opinion, 8 percent.

Q. "Most members of Congress care more about keeping power than they do about the best interests of the nation."

A. Agree, 64 percent; disagree, 28 percent; no opinion, 8 percent.

These results are striking, even though it has long been conventional wisdom that citizens hold Washington politicians in low esteem. Presidents Reagan and Carter, among others, have won elections by running against official Washington, and especially against Congress.

On the face of it, there is little difference in the anger expressed toward Congress by voters and nonvoters, except for one significant divergence:

Voters are much more likely than nonvoters to believe that there is a great deal of difference between the two major political parties. Three in 10 habitual voters take that view, while only half that proportion of nonvoters subscribe to it.

Nonvoters, on the other hand, are more likely than voters to feel that there is hardly any difference at all between the two parties. Four in 10 nonvoters feel that way, compared to 3 in 10 voters.

To some extent, many people continue to go to the polls because they feel they have to -- that their vote is important -- and not because they like the choices offered them. And growing numbers appear to be concluding, regardless of what they learned in civics class, that their vote is not important after all.

As for just what the electorate will look like in the 1982 congressional election, here is what the Post-ABC News poll suggests:

Only 14 percent of those younger than 30 are likely to vote. Above that age, participation will pick up sharply, with 39 percent of people between 31 and 60 voting. And among those older than 60, a majority of 53 percent may be expected to vote.

Women will vote at the same rate as men or even in a slightly higher proportion, a reversal of tradition. The survey, in which 1,505 people were interviewed, suggests that turnout will be 34 percent among women and 32 percent among men. But that difference falls within the margin of sampling error for a poll of that many people.

Among citizens who consider themselves working class, the expected turnout, as of now, will be 29 percent, and for the middle class 42 percent. By race, 35 percent of whites are likely to vote but only 26 percent of blacks. There is little variation by region , although residents of the East appear more likely to vote than those in other regions.

People who work for local, state or federal government are more likely to be voting than nongovernment workers, and union members will turn out in somewhat higher numbers than the population at large. While Republicans usually benefit from low-turnout elections, the poll suggests that this time, even with a very low vote, Democrats and Republicans may be voting in the same proportions.