Thanks to the Merrimack County Republican committee, Sen. Howard H. Baker Jr. (R-Tenn.) now has what every presidential hopeful here needs: a New Hampshire survival kit.

Presented with a great deal of fanfare and some gentle ribbing the other night, it includes: a "reliable pair of earmuffs," a supply of New Hampshire apples and pure maple syrup, a pair of "bought-in-New Hampshire-galoshes" (for all those stories that begin "sloshing through the snow...") and the telephone number of the Dixville Notch, N.H., selectman (to find out how many votes Baker gets there).

It is a full year before the voters in Dixville Notch, which casts its 26 ballots on the stroke of midnight each election day, and the rest of New Hampshire open the 1980 presidential sweepstakes. But the race for the Republican nomination has been under way here for months.

"Half the candidates are trying to act like Jimmy Carter did, and the party activists are afraid they won't sign on with someone soon enough," says one party leader. "People are worried if they don't get in early they won't be kingpins."

Baker's GOP rivals have spent so much time and enlisted so many supporters that when the Senate minority leader made his first extended visit here last week, he was worried that there wasn't anyone left of importance for him to recruit.

He says that turned out to be untrue.

However, there has been considerable maneuvering. Ronald Reagan remains the early favorite here, but repeated visits by George Bush, Rep. Philip Crane (R-Ill.), and to a lesser extent, Sen. Bob Dole (R-Kan.) have made a mark. Several key Reagan workers from his 1976 primary campaign are courting other candidates; others worry that the former California governor, who is 67, is too old for the presidency.

Bush, a former ambassador and Texas congressman, has gained the support of key moderate party leaders. Crane has gained credibility by picking up parts of the organization that help elect fellow conservative Gordon Humphrey to the U.S. Senate last fall and has been making minor inroads among former Reaganites.

But the political situation here remains fluid. It's best captured by random anecdote:

John Connally, almost everyone here agrees, is a wildcard in the New Hampshire primary. No one knows quite what to expect from the former Texas governor and treasury secretary. So what's he up to?

Connally is looking for land to buy in New Hampshire. Preferably a big place with a view, mountains and a couple of hundred acres close to ski slopes and an airport.

"I told him we could run him as a favorite son up here," says Allan Parker, Connally's unofficial contact man here. "It would be a dashing move that only a guy like Connally could pull off. He could use it for campaign entertaining -- Texas barbecues and such -- and to be close to the scene. I think it's a great idea."

Connally, who formally declared his candidacy last month, wants a place large enough to house his children and grandchildren during family vacations, according to real estate agent Martha Corson, who has kept in touch with the Connallys since last fall.

Politics is obviously a part of the appeal of New Hampshire for Connally, she said. "He probably still wouldn't be interested if he hadn't announced. I really expect to hear from them again soon."

The archconservative Manchester Union Leader, the statehs largest newspaper, and its editor, William Loeb, are out for Crane's neck, and have suggested that he drop out of the race. That's a good sign for Crane, says Rep. James C. Cleveland (R-N.H.).

"Crane must be doing pretty well or Bill Loeb wouldn't be telling him not to run," said Cleveland, who is supporting Bush. "It indicates to me that Crane is cutting in on Reagan.

In a signed, front-page editorial Feb. 9, Loeb accused Crane of "playing the spoiler's role" in New Hampshire and trying to split the "conservative, sensible vote."

"Someone should break the news to Crane that good looks and a Ph.D. are simply not sufficient qualifications for running for president," Loeb said. "We need someone such as Reagan who has successfully governed the largest state in the Union for eight years. He is mature and knows what he is doing.

"We have had enough of boy wonders, either from Plains or from Illinois, where Crane hails from," he added. "This nation does not need any more glamorous amateurs in the White House."

A year before the primary, there is little obvious Reagan activity. The conventional wisdom is that there doesn't have to be.

Former governor Meldrim Thomson offered to head Reagan's campaign when he saw him last June. But Thomson, an archconservative, hasn't heard from Reagan or his staff since, and he's miffed about it.

Former governor Hugh Gregg, the 1976 Reagan chairman here, has told Reagan he won't work for him this year and he's talked to Bush about playing a major role in his campaign. Stewart Lamprey, an old party pro whose computerized voter list was used effectively by the Reagan forces in 1977, arranged Baker's visit here last week.

If you want to stop any conversation here dead in its tracks, try suggesting that the Puerto Rican presidential primary may be more important than the one in New Hamsphire in 1980. After all, the Puerto Rico primary is scheduled just before the traditional first one here, has more delegate votes at stake, and would be a warmer place to campaign.

The usual reaction to these arguments is a prolonged sputter. Presidential politics here is regarded as a valuable natural resource, high sport and good business. The state isn't going to give it up without a fight. One approach, incorporated in a bill pending in the state legislature, would be to move the primary up a few weeks. Another is to badmouth Puerto Rico.

"I don't speak Spanish and I don't think anyone who doesn't is going to go anywhere in Puerto Rico," says House Speaker George Roberts, a Republican. "That's going to be a single-issue primary which a Spanish-speaking favorite son will win by talking about statehood. New Hampshire doesn't have anything to worry about."

Republicans in New Hampshire believe Jimmy Carter is in deep trouble and many Democrats are uneasy with him. The state's Democratic senator, John A. Durkin, has been critical of Carter in recent weeks. A number of Democrats are privately talking about joining a write-in campaign for Sen. Edward M. Kennedy (D-Mass.), and the Democratic chairman in New Hampshire's most populous county has invited California Gov. Edmund G. (Jerry) Brown Jr. to visit in the spring.

"I don't think it's outright dissatisfaction with Carter. I think it's more disappointment that he hasn't kept his promises," says Romeo E. Dorval, the state Democratic chairman. "Between now and 1980 his record has to improve."

Dorval has invited Carter to a statewide fund-raiser late in April. Jack Meehan, the Hillsborough County Democratic chairman, has asked Brown to drop by the following month, and he speculates Brown will draw a bigger crowd.

"The president has real problems here, but so far his people have ignored them," Meehan says.