In a single night, New Hampshire rejuvenated the faded fortunes of Ronald Reagan and all but buried the once bright hopes of Edward M. Kennedy.

Reagan can now ride his landslide southward looking like the front-runner he always thought he was. Even George Bush's stunned advisers were conceding that tonight had wiped out the lead their candidate had counted on in next week's primaries in Massachusetts and Vermont, and the following week's contest in Florida -- "our best state in the south" -- in the words of Bush campaign manager James Baker.

It is conceivable that Republican Bush, who still has plenty of campaign money, may head into those states and still give Reagan a good battle. But it appears that Kennedy, whose campaign is virtually broke, has no good place to go.

Kennedy can carry President Carter into the Kennedy family's home state of Massachusetts and probably score a victory, but that will impress no one outside the state. After that comes the South, which is Carter country, and then comes Illinois, which once looked like the place where Kennedy could wrap up the nomination.

That was before the Carter strategists stripped away most of his potential support, leaving Kennedy with only Chicago Mayor Jane Byrne and remnants of her machine.

For the Democrats, the New Hampshire campaign followed a pattern of no change. Kennedy waged campaign efforts that were uneven, and could not even make his major issues -- anti-inflation, controls on wages and prices -- catch on, despite the Carter administration's severe problems in handling the economy.

But if the Democratic race represented no change, the Republican race was something else.

While the conservative candidacy of Reagan was being reborn, the results left unclear just what would be happening in the moderate segment of the Republican Party. Both Bush and Howard Baker had viewed themselves as the chief competitors for the title of being the moderate alternative to Reagan. But the votes Bush apparently lost in the last few days went to Reagan, not to Baker.

So while Bush claimed tonight that it is now a "two-man race," and while Baker may be reassessing, it is possible that some moderate Republicans will look with renewed interest at a man who has not campaigned at all in 1980, former president Gerald R. Ford. Several of those close to Ford have at varous times tried promote the notion of a Ford candidacy, but Ford has so far showed no inclination to campaign.

Conceivably, there will be a new Ford drive now, after a primary that was decided in the last days when Ronald Reagan built a political trap around a debate and George Bush stepped into it.

As New Hampshire saw it, Bush first refused even to talk to his fellow candidates, then he did not debate them, and finally he left the state three days before the election, choosing not to campaign so that his organization could be free to get out the vote.

All of this seemed to reinforce the very image problem Bush has fought to overcome; that he is just the sort of preppie, Yalie, Skull and Bones Society fellow his biography says he is. All of Bush's Republican opponents were hollering that he was arrogant, and that is the way it looked.

A contest all of the polls were showing as virtually even between Reagan and Bush just days earlier suddenly crumbled before the Bush advisers knew what was happening to them. And Ronald Reagan, who stayed in the state and campaigned, found himself sitting atop a landslide election night.

It was one of the classic miscalculations of presidential politics, as grievous a series of errors in its own way as Sen. Edmund S. Muskie's moment of crying in the snow proved to his 1972 campaign.

The chain of events by which George Bush did himself in began with a Saturday night event that was billed as the great Reagan-Bush debate, but which looked more like Saturday Night Live. Before it was over, the statesmen of the Grand Old Party had performed like the slap-stickers of the Grand Ole Opry, and George Bush was a frontrunner fallen flat.

First Bush's campaign manager, and then Bush, himself, made crucial errors of judgment. "I was out-Machiavellied -- I concede that," James Baker said in an interview. And the Machiavelli who did him in on behalf of Ronald Reagan was none other than John P. Sears, the campaign manager who Reagan was in the process of firing today, even as his landslide victory was occurring.

Just minutes before the debate Saturday, Regan sent word to Bush that he wanted to talk with him about expanding the debate to include all the candidates. Baker went to meet with Sears about it. Baker said he told Sears that Bush preferred to debate Reagan one-on-one, but that the matter should really be decided by The Nashua Telegraph newspaper, which was sponsoring the event, and Reagan, who was paying for it. Baker said there was no reason for Bush and Reagan to meet because Bush would be willing to abide by whatever ground rules they agreed to.

The Bush campaign manager said that as he left this meeting and walked down the hall of the Nashua High School, he looked into Reagan's room and saw all of the other Republican candidates still in New Hampshire -- John F. Anderson, Howard H. Baker Jr., Philip M. Crane, and Bob Dole. Here Baker made his major error. He did not go in to talk to them, but let the Reagan campaign manager communicate with the other candidates for him. He went back to Bush and reported that the meeting with Reagan would have in fact been "an ambush" with all the other candidates.

Meanwhile, according to Dole, the candidates in the room received a rather different picture of Bush's position.

Dole said that an aide -- he recalls that it was Reagan's press secretary, James Lake -- came into the holding room and told the candidates: "George won't meet with us."

The effect was like pouring gasoline on smoldering coals. Dole suggested that they send Sen. Gordon J. Humphrey to carry the message to Bush. The two met just as Bush was walking up to the stage, and when the freshman New Hampshire senator told Bush that what he was about to do was not good for the Republican Party. Bush responded that he had done more for the Republican Party than Humphrey ever had.

By the time that was reported to the other candidates, the excluded men of the GOP were ready to take on Bush like the Gang of Four, which is precisely what they did.

Looking back, James Baker said, "I don't think there's any doubt that what happened on Saturday night and after that hurt us severely."