MANCHESTER, N.H.--Reacting to results which barely distinguished winners from losers, candidates for the Democratic and Republican nominations yesterday all acted like victors as they promised to build on their showings in the nation's first primary.

Former Mass. Sen. Paul E. Tsongas, the Democratic winner, said his victory was a triumph for economic realism.

"I'm not running to be Santa Claus. I'm running to be president, and there's a difference," said Tsongas, referring to his opposition to the middle-class tax cut proposed by Bush and his Democratic rivals.

Tsongas, speaking before an uproarious crowd at Razzberrys Restaurant, tried to distinguish himself further from his more liberal opponents.

"You can't be pro-jobs and anti-business at the same time," said Tsongas, who admitted he needs a strong showing next week in the South Dakota and Maryland primaries to prove he is more than a regional candidate.

"You cannot love employment and hate employers," Tsongas said.

Tsongas' aides agreed and said his challenge now is to expand his campaign in to the South and the West, where he is relatively unknown.

"He feels very overwhelmed that New Hampshire got behind his message," said Peggy Connolly, Tsongas' press secretary. "And it gives him the confidence to leave New Hampshire and tell it to the rest of this country."

A similar task confronts Republican challenger Patrick J. Buchanan, who won more than 40 percent of the vote yesterday.

"We are going to take our party back," said Buchanan, who plans to campaign in Georgia, Texas and Louisiana later this month.

"And when we take our party back, we'll take the country back," Buchanan told an enthusiastic group of supporters who chanted, "Read our lips, no second term."

But advisers said that regardless of how Buchanan fares in other states, his showing here is a warning to President Bush.

"This is a strong signal to the American public," said Angela Bay Buchanan, the candidate's campaign manager and sister.

At a campaign celebration in Merrimack, Arkansas Gov. Bill Clinton said he was proud of his second-place showing and of his rebound from recent polls that showed him trailing Tsongas by as many as 20 percentage points.

"I think we know enough to say that New Hampshire tonight has made Bill Clinton the come-back kid," he said.