Early on the morning of Election Day, Allard K. Lowenstein was trying to get Long Island commuters to stop and shake his hand. In between trains, he quietly picked some of his campaign literature out of the garbage pail. A heavy-set man wearing a Nixon button glared at one of the girls helping Lowenstein. "I'd never vote for him," he said. "I'm a policeman."

Lowenstein, the Democratic-Liberal candidate for Congressman from Nassau Country's fifth district, was exhausted Tuesday. His clothes were rumpled, and his hair kept slipping down over his forehead. He was running against Mason L. Hampton Jr., a Republican-Conservative and often called "the Wallace of Nassau Country."

"Hampton helps us," Lowenstein said Tuesday afternoon, sipping a Coke in a luncheonette. "Hampton helps, like Nixon helps and Agnew helps. Republicans are really useful for helping Democrats."

Hampton is a founder of New York's Conservative Party. He received the Republican endorsement as the result of a deal in which the Conservatives agreed to support the Republican candidate for District Attorney.

Hampton's headquarters in Baldwin, L.I., are right across the street from the Lowenstein storefront, but the people inside don't even look the same. Inside Lowenstein's storefront, phones are ringing, people are shouting, women are serving coffee. High school kids are running out to polling places to distribute Lowenstein-O'Dwyer literature. Among the campaign posters on the walls are charts and maps of the district.

In Hampton headquarters, however, nothing happens. The posters are all of Nixon. The three kids in the room look like the ones in high school who chew gum too loudly and think it's really funny to wear Alfred E. Neuman sweatshirts.

Hampton based his campaign on the Conservative Party platform, which he helped to draft in 1966. He supported an unconditional victory in Vietnam, drastic cuts in state and federal aid to education, a curtailment of federal spending and "systematic reduction in the size and cost of government."

During the campaign, Hampton also accused Lowenstein of advocating the legalization of marijuana, although Lowenstein did not in fact do so. Hampton proposed the death penalty for dealers, and life imprisonment for use of the drug, and his supporters often went down to the Lowenstein headquarters in Rockville Centre and asked students working there, "Do you really smoke pot?"

Lowenstein, commenting on Hampton's position, said, "I oppose the death penalty." He laughed.

By contrast, Lowenstein ran his campaign with storefronts in all Fifth District towns, manned mostly by Jewish mothers and high school students. The workers, canvassing their neighborhoods, opposed Hampton on every point. They called for the unconditional cessation of the bombing of North Vietnam and the formation of a representative coalition government in South Vietnam. Lowenstein himself denounced the war as "the greatest tragedy of American foreign policy in many decades."

He also supported enactment of a guaranteed job program, an increase in welfare grants, and the introduction of welfare clients into the program's administrative structure.

Lowenstein's district headquarters fill the top floor of a rented Rockville Centre office building. Some of the walls in the office are green, some are yellow, and all are dirty and covered with posters. Boards and old newspapers litter the floor. In the back are tables lined with telephones; in the front is a press area with files and photographs of Lowenstein and his family. The ceiling looks like it leaks. A poster on the wall shows Humphrey saying, "Let's Stop Pretending that Mayor Daley Did Anything Wrong in Chicago." There are no HHH buttons in sight.

Lowenstein finally did endorse Humphrey, announcing his support for the Vice-President immediately after Johnson stopped the bombing.

"If I had failed to endorse him I would have been a hypocrite," Lowenstein said Tuesday. "I had said that I would support him if there was some change in the administration's Vietnam policy. I really had no choice." Many of Lowenstein's student supporters were angry at the move, but none were upset enough to desert their candidate.

On Election Day they handed out sample ballots highlighting Lowenstein's name at the polling places, but they didn't have an easy time of it. In Baldwin one boy was arrested for standing too close to the polling place, even though he was outside the 100-foot marker. The police claimed that the marker was in the wrong place.