In the midst of the Washington area's most vitriolic congressional race, an earnest young man blinks owlishly and chastises both his opponents like a high school civics teacher disappointed with democracy in action.

Austin W. Morrill Jr., 33, is the Citizens Party candidate in Northern Virginia's 8th District, where Republican Rep. Stanford E. Parris and Democrat Herbert E. Harris II will also appear on the ballot Tuesday. Although polls show most voters have never heard of Morrill, the two major candidates are taking him almost as seriously as he takes himself.

"Obviously, virtually any vote for Morrill is a vote for Parris," says former representative Harris, who was narrowly defeated by Parris two years ago when an independent, promarijuana candidate captured more than 5,000 votes. "If you have a close race, anything like that can become significant."

Some Republicans apparently agree. After one bitter debate in Springfield, Fairfax County Board Chairman John F. Herrity, a Parris backer, waved goodbye to Morrill, urging him "Keep up the good work."

Morrill says he is running to promote a freeze on nuclear weapons, although he sometimes neglects to mention the issue in debates. He says he doesn't mind being a spoiler.

"I have to be personally accountable to myself," says Morrill, who is unemployed and says he is living off his campaign contributions. "If we have a nuclear war, I'm going to be able to say I made a significant contribution toward having it stopped."

The third party candidate in the neighboring 10th District, Libertarian Scott R. Bowden, 28, a data processing consultant, says his mission is to educate the voters about his party, which advocates that the government withdraw from economic, moral and military affairs. Bowden says he expects to receive about 3 percent of the vote and acknowledges he is unlikely to be a factor in the race between Republican Rep. Frank R. Wolf or Democrat Ira M. Lechner.

Bowden has been ignored by both Wolf and Lechner and has been barred from some debates. "High school seniors are most receptive to my message, because they haven't been indoctrinated yet," said Bowden, who maps strategy with 25 other Libertarians during monthly dinner meetings at a Bob's Big Boy Restaurant in Arlington.

His call for eliminating taxes, which he labels "a form of legalized theft," often is greeted with approving laughter at candidates' nights in Arlington, northern Fairfax and Loudoun counties. His suggestions that drugs and prostitution should be legalized, federal employes fired and neighborhoods left to buy their own anti-Soviet missiles usually are met with stony silence.

While his media-conscious opponents dress in dark business suits and blue shirts that look good on television, Bowden, with his Chekovian bushy brown beard and bright green socks, is less conventional.

"There is very little difference between the Republican and Democratic parties," said Bowden. "There's a very clear choice and that's the Libertarian choice."

When he began his campaign in the 8th District, which includes Alexandria, and portions of Fairfax, Prince William and Stafford counties, Morrill's inexperience showed. He would often end his speeches with hesitant recommendations of books by environmentalist Barry Commoner and get bogged down explaining the connection between child nutrition and unemployment. His style has improved, however, and Morrill now draws enthusiastic cheers when he criticizes both Harris and Parris for attacking each other without offering solutions.

Harris, who stands to lose more than Parris if liberal voters support Morrill, has sometimes ignored Morrill and sometimes belittled him. After Morrill attacked him during a debate in Prince William County, Harris recited a verse from a 18th century poem: "And still they gazed, and still their wonder grew, that one small head could carry all he knew."

Said Morrill later: "I think he was trying to say that people who support the bilateral freeze are simple-minded."