The major Republican contenders conferred with their staffs today about how to adjust to a presidential world in which Ronald Reagan has been reanointed the front-runner.

George Bush's advisers spent part of the day analyzing what went wrong in Tuesday's voting and setting out a more aggressive strategy for their candidate. Howard Baker conferred in Washington with his advisers, who also devoted the day to looking for John Sears, ousted on Tuesday as Reagan's campaign chief.

"We've left messages for him all over town," said one Baker adviser.

Both staffs were searching for a way to bring the high-flying Reagan back down to earth.

They will have their first chance Thursday night in Columbia, S.C., where they and John B. Connally will join Reagan in a televised debate that is preliminary to the March 8 South Carolina primary.

Sen. Bob Dole, who was scheduled to participate in that debate, pulled out today and began staff reductions in what appeared to be a phase-out of his grounded presidential campaign.

Rep. John B. Anderson, who finished fourth in New Hampshire and third behind Reagan and Bush in Tuesday's Minnesota Caucuses, focused his campaigning on next Tuesday's Massachusetts primary, vowing to "keep going as long as I have clean laundry."

Rep. Philip M. Crane, another of the GOP stragglers, said he would continue campaigning in Massachusetts, but added he might join forces later with fellow-conservative Reagan.

In a post-debacle strategy meeting, Bush's top advisers decided today that Bush should begin attacking Reagan head on, with issue-oriented thrust, if he is to catch the rejuvenated Republican front-runner.

But the Bush advisers concluded, in a session their candidate did not attend, that they did not know if Bush was willing to attack Reagan in such a manner nor even if he was constitutionally capable of doing it.

The post-New Hampshire phase of the 1980 Republican presidential campaign quickly hit its stride, and this became clear by the time this session had ended. Bush will be going all-out to win next Tuesday's primaries in Massachusetts (where Republicans are moderate) and Vermont.

Reagan, meanwhile, will be hoping to win in those states but will be looking mainly to the following week's primaries in South Carolina, Florida, Georgia and Alabama to put together a series of victories that will enable him to wrap up the next round of primaries in the industrial states of the North and Midwest.

One of the few bright spots for the Bush advisers as they congregated this morning in the candidate's empty hotel suite here was money. Bush has spent $8.6 million so far, according to press secretary Peter Teeley, which means the former U.N. ambassador has much more leeway than Reagan before running into the federal spending ceiling.

The manner of the advisers is said to have been businesslike and not as despondent as a post-mortem of their i7 percentage point drubbing by Reagan might have led them to be.

Attending the meeting were Bush campaign manager James Baker, his pollster Robert Teeter, national political director David Keene, Teeley and issues adviser Stefan Halper.

According to several of those present, Baker began by saying, "I've got three things I want to talk about -- scheduling, polling and issues." Teeter played a major role in the discussions. "We've got to show that we can win in Massachusetts" he said, according to several sources.

The advisers agreed Bush must concentrate on Massachusetts and Vermont in the hopes of finding his lost momentum.

They agreed to scrap a day's worth of visits in the coming week to Alabama and Illinois and canceled a weekend of rest that had been planned for Bush in Houston so the candidate can campaign in these two states.

Bush's lead was once strong in Massachusetts; but in the wake of New Hampshire, the advisers concluded, the lead is probably gone. Vermont is a more conservative state, where Bush used to hold a small lead in the polls. But that too probably has vanished.

Still, the advisers reasoned, Bush has a better chance of regaining his winning ways there than in Florida. If Bush does not win in New England, he has virtually no chance of carrying Florida a week later they believe. Before New Hampshire, Teeter had taken a poll showing Bush ahead by four percentage points. Now, they decided, Teeter will do another poll in Florida to see just how far the landslide damage from New Hamsphire has slid.

Then the advisers moved on to the issues, which quickly became a discussion of strategy.

Teeter took the view that Bush must try to focus an attack directly on Reagan and that he must do this by hitting Reagan on substantive matters.

This would be a distinctive shift of style for Bush, who has stressed such themes as optimism-for-the-eighties in his stump appearances.

They outlined several areas where Reagan could be attacked. The most prominent was Reagan's recent comments that the storage of nuclear waste should be best handled by private industry. This, they said, raises considerable questions, that Reagan should be asked about safeguards against leakage of contaminated material, theft by terrorists, sabotage, and the self-interests of corporations that could at times conflict with the public welfare in the costly disposal of dangerous radioactive material.

One adviser pointed out that South Carolina -- where Reagan and Bush and other candidates are to debate Thursday night -- is one of three states which are dumping sites for nuclear waste.

The advisers talked of how Bush should, as one said, "hit Reagan right between the eyes" by comparing Reagan's limited foreign policy experience with that of Bush. Another recalled a Reagan position that the management of welfare should be returned to the states and that this could be financed by returning "sources of tax revenue" to the state. He urged that Bush press Reagan to state specifically what sources of revenue he had in mind.

"But there was a question as to whether George would be willing to take Reagan on full blast when they go head-to-head," one adviser conceded. Others said no one spoke out with conviction that Bush would be willing to adopt the tack they all seemed to favor.

Howard Baker, making the best of his third-place finish, told reporters in New Hampshire today that his 13 percent of the vote made the Republican nomination a three-man race.

"I'm never satisfied, but it was certainly far above what the minimum was to stay alive," Baker said. "I think the political situation right now is very volatile. . . . I expect that you'll see the front-runner status change time and time again in the next few weeks and months."

Baker flew to Washington for a campaign strategy meeting attended by Gov. Robert Ray of Iowa, Gov. Richard Snelling of Vermont and former governor Walter Peterson of Tennessee.

"We are preparing for a sustained and lengthy campaign," said Sen. Richard Lugar, Baker's campaign chairman, after the meeting. "I think our campaign is resonably well-paced for the long run. We were faulted for starting late, but in the long run Howard will probably be in a stronger situation."

Lugar declared that Bush's campaign has peaked. "New Hampshire indicated that a campaign can't be built on enthusiasm. Bush has no ideological base, no particular positions that voters could identify as reasonable."

Lugar said the campaign is about $500,000 in debt and has spent about $4 million. "We have some comfort in the fact that most of our competition is in a similar predicament."

Baker aides tried in vain yesterday to reach John P. Sears, the political strategist who was fired as Reagan's top campaign official Tuesday. "Obviously we'd be delighted to have him come and help us out," said Douglas Bailey, Baker's media adviser. "There is more brainpower in that one human being that in most of the political campaigns combined."

The name of former President Ford was brought up with some frequency in the freshly scrambled GOP picture.Dole, who was Ford's runningmate in 1976, predicted the New Hampshire results would lure Ford into the contest, which he has often said he will shun -- unless drafted.

"I would guess you'll be hearing from President Ford," Dole said.