BERLIN, N.H. -- Paul Laxalt was up before 6, in time to greet the early shift outside the big James River Co. paper mill here. With clouds still clinging to the green ridges that flank this picturesque valley, he dutifully smiled and shook hands with the bleary-eyed workers, remarking after one man had passed that "the last guy he wants to see is somebody running for president."

It may also have been about the last place that Laxalt, the former two-term Republican senator from Nevada, wanted to be at that hour. But he is running for president and one purpose of the ritual, early-morning plant-gate visit was to demonstrate to skeptics that he is willing to do what is needed to win.

During a three-day swing through New Hampshire last week, it was evident that Laxalt's late-starting campaign brings to the GOP contest some of the strengths and weaknesses of the candidate's close, personal friend, Ronald Reagan.

Laxalt's ties to Reagan, which include national chairmanship of Reagan's three presidential campaigns, provided him with access to a waiting network of conservative activists who see the Nevadan, not Vice President Bush, as the president's true heir.

Laxalt's national campaign organization is studded with prominent Reagan loyalists. His New Hampshire chairman is Meldrim Thomson Jr., the archconservative, former governor of this key state and one of Reagan's strongest boosters.

Like Reagan, Laxalt is an affable, easy-going westerner whose reputation for seldom exerting himself is being exploited by his rivals. At one stop in Nashua, Laxalt was questioned by a reporter about rumors, which he denied, that he has refused to campaign on weekends.

New Hampshire's most conservative Republicans are desperately searching for a tough, hard-charging challenger to take on Bush and Senate Minority Leader Robert J. Dole (R-Kan.), the presumed front-runners. Six months before they vote in the first presidential primary of 1988, they remain to be convinced that Laxalt, with his relaxed personal style and gentlemanly, almost diffident rhetoric, is right for the job.

New Hampshire, linchpin of Laxalt's campaign strategy, is a critical test. This month and next, he is to spend 10 days here and only two in Iowa, a good indication of the importance his staff attaches to the two states that begin the nominating process.

In New Hampshire's Feb. 16 primary, Laxalt hopes to eliminate Rep. Jack Kemp (R-N.Y.), emerging as the conservatives' "umbrella candidate" and the alternative to either Bush or Dole as the campaign heads South and later West, Laxalt's home region.

"There are really two primaries up here," said Gerald P. Carmen, Laxalt's national campaign chairman and a former New Hampshire GOP chairman. "The first primary is between the two front-runners, Bush and Dole. But the real winner will be the one who wins the other primary and comes out of the pack to be the umbrella candidate."

Carmen and David A. Young, a state representative and executive director of Laxalt's New Hampshire campaign, concede that Bush is far ahead here. But they argue that Laxalt's strategy has the ingredients for success.

One pillar of that strategy is Thomson, a revered figure of the GOP right. The spry 75-year-old campaigned side by side with Laxalt last week and said he is continuing to push the candidate to take the kind of "very strong positions" that appeal to the state's conservatives.

Asked about the state of the Laxalt campaign, Thomson replied impishly, "embryonic," but promised that it would grow. "He's going to get so good you won't like it," Thomson said.

The second, and missing, pillar is the support of Nackey S. Loeb, publisher of the Manchester Union Leader, New Hampshire's dominant daily newspaper and the voice of the state's most strident conservatives. Thomson concedes that "it would be very difficult" for Laxalt to succeed here without the newspaper's support.

Loeb has not found the candidate best suited to assault Bush. She and her editorial board met with Laxalt for more than an hour, questioning him closely about the U.S.-supported peace initiative in Central America, which the newspaper abhors.

She was quoted later as saying Laxalt is "a nice person" but "doesn't push hard enough." Moreover, Loeb, thought to be unimpressed by Kemp, sent a shudder through the Laxalt campaign by suggesting in a front-page editorial that New Hampshire Republicans "take a good look at" another dark horse, former Delaware governor Pierre S. (Pete) du Pont IV.

According to Young, du Pont has worked this state harder than any GOP contender, and Thomson said he has been particularly adept at "courting" Loeb.

It remains to be seen whether Thomson can push Laxalt into the kind of campaign he envisions. Unfailingly courteous and good-humored, Laxalt said he refuses to be "intrusive" while campaigning. At the Choo Choo Diner here after the plant-gate visit, Thomson had to urge Laxalt to introduce himself to customers eating breakfast at the counter.

By temperament and style, and because of his deep personal loyalty to Reagan, Laxalt may find it difficult to wage the kind of campaign that Thomson and the Union Leader seek.

Kemp has denounced the Central America peace initiative as a "sellout" of the Nicaraguan contras and "a policy of appeasement." Laxalt, too, is critical and urged continued support of the contras but in terms that did not approach Kemp's fiery rhetoric on the contra cause.

A similar lack of sharp focus was evident in Laxalt's pronouncements during the campaign tour. Among his central themes is the danger posed by the federal deficit, a tactic aimed directly at Kemp, the most ardent hopeful who advocates supply-side economics. Especially in tight-fisted New Hampshire, "people don't believe we can grow our way out of the deficit," a Laxalt campaign aide said.

Laxalt, like Kemp and the others, adamantly opposes a tax increase to reduce the deficit. He parts company with his rivals in suggesting that many necessary spending cuts could come from unspecified freezes in the defense budget, but he also supports the president's missile defense plan, the Strategic Defense Initiative.

Speaking to the Londonderry Rotary Club, Laxalt defended Reagan's failure ever to submit a balanced budget to Congress. In the economic conditions of the time, he said, a balanced budget would have provoked "a near revolution in this country."

During a television interview the same day, Laxalt blurted, "I would immediately submit a balanced budget." Asked later how he could do in one year what Reagan has not done in six, he said only that the Reagan military buildup was complete and that "conditions are different."

"It's tough for senators," Laxalt said, acknowledging that the Senate's elaborate rituals of courtesy and decorum are not the best training for presidential-campaign rigors. "As a senator, you have everything greased for you. This is pick-and-shovel work."

Although deeply conservative, Laxalt was popular in the Senate, even among liberal Democrats, whose friendships he valued and returned. Within his first 24 hours in New Hampshire last week, he managed to comment favorably about the Democratic chairmen of the Iran-contra investigating committees, Sen. Daniel K. Inouye (D-Hawaii) and Rep. Lee H. Hamilton (D-Ind.), and two former Democratic Senate colleagues, Mike Mansfield (Mont.) and the late Hubert H. Humphrey (Minn.).

These names do not inspire the confidence of Loeb and the right wing of the New Hampshire GOP.

"I catch hell from my political people for not being bluntly political and partisan," Laxalt said. "I've never done it in my political life, and I'm not going to start now."