MANCHESTER, N.H.--Headquarters here were deserted last night as candidates, press and campaign workers retired to ballrooms and press lounges throughout the city to await returns from yesterday's primary.

While Republicans in Concord watched President Nixon's lead grow through the night, a decision in the Democratic race was not as clear. Frontrunners Edmund S. Muskie and George McGovern could both claim victory and both election centers reflected enthusiasm.

The Muskie staff, working feverishly through the day to get out the vote, was noticeably tense. "If you're not working for us, we don't want you here," one staffer said in the state headquarters.

By 9 p.m. the tension had not subsided. Barry Wanger, State Press Secretary, assessed the incoming Manchester votes for reporters, and conveyed Muskie's disappointment. Wanger indicated that Tony Podesta, Muskie's chief New Hampshire coordinator, "felt that the Manchester Union Leader had a lot to do with Muskie's poor showing here." He pointed to overall state returns (48 per cent for Muskie at that time) as a more encouraging and accurate picture of the race.

Downstairs in the ballroom of the Sheraton-Carpenter Hotel, a crowd of some 400 jubilant Muskie supporters seemed oblivious to the concern in the press room. A band played cheerful music under the bright glare of television lights and a predominantly young crowd roared with delight as the first returns were posted.

Over at the McGovern election center in Howard Johnson's Motor Lodge, a crowd of reporters heard the South Dakota Senator claim a "moral victory." Asked if he had been the main factor in Muskie's less-than-expected performance, McGovern said, "Well I don't think there's any question about it. I'm emerging as the leading challenger to Ed Muskie."

McGovern cited the Manchester returns as a refutation of the claim that his is a one-issue candidacy. "We're running strong in Manchester, which is a highly blue-collar town." he said.