As legislators trickled out of the State Capitol and darkness fell, Gov. John N. Dalton left a desk still thick with governmental business last Thursday and headed with his wife Eddy for nearby John Marshall Hotel and some very different business.

It was there, in a chandeliered banquet room lined with portraits of famous Virginia statesmen, that the John Dalton most people here say they will remember emerged: Less a governor who brought new vision to an office he considers one of the most powerful in the nation, than a party leader who ran one of the most effective political machines in the nation, the Virginia Republican Party.

In his speech at a Republican fund-raiser that night, Dalton, recalled the 1960s when there were but six Republicans in the 140-member General Assembly -- "You literally could hold your meetings in a phone booth," he quipped later - and noted the increase to 34 today and the party's dominance of the state's major elected offices and its congressional delegation. And he told the cheering crowd: "With your help, we're going to have many more Republicans in the legislature in times to come . . . we'll be in control in the near future."

As he enters his fourth and final year in office, Dalton is confident that he has fulfilled his mandate as governor to cut down the growth of state government and appears most certain of leaving a legacy of political success for his party and the man he has decided should succeed him, Republican Attorney General J. Marshall Coleman.

Dalton's critics say his administration will be judged at best as a lackluster, caretaker regime. "He'll go down as the state's third Republican governor and that's about it," says Del. Frank Slayton (D-South Boston).

There are others who believe the Dalton administration's legacy will be one of indifference to the state's pressing social problems. They point to his veto of Medicaid funding for abortions due to rape or incest, cutbacks in Medicaid payments and the scrapping of a federally funded program for the mentally disabled as evidence.

"In the area of services to the elderly and handicapped and services to all who are poor or sick, he's shown a determined hostility," contends Del. Mary Marshall, an Arlington Democrat.

But Dalton sees himself vindicated by the one test he believes deeply in -- the ballot box. He argues that Virginians approve of what he has done and that Ronald Reagan's victory is proof that his own approach to government is the wave of the future.

"I don't think you can satisfy everybody's desires and still do what we've done in cutting back," he said. "You can't have it both ways and I feel that the message I'm getting across Virginia and across the nation . . . [is] that people are not looking to continue the expansion of government."

The confidence with which Dalton spoke of his administration in a private interview Friday morning in his third-floor office in the Capitol was in marked contrast to a melancholy tone that was very much apparent on other, more personal subjects.

Part of it stems from the recent suicide of his chief aide, Larry E. Murphy, who had served Dalton as both loyal guardian and confidante for six years. While the office still runs smoothly, Dalton said, Murphy's death has left him troubled and saddened.

"It's affected me personally very deeply," said Dalton. "I hardly have a night that I don't wake up sometime during the night thinking about it. I look back and try to figure out what I could have done that might have changed the situation."

Another puzzle is the question of Dalton's own future. At 49, he is hardly ready for retirement. He is also keenly aware that most former Virginia governors have found their prospects extremely limited. Unless U.S. Sen. Harry F. Byrd Jr. decides not to run for reelection next year, Dalton may find himself consigned to a second-level job in the Reagan administration or retired to the life of a country lawyer in his native mountain home of Radford.

"Personally I think it [leaving office] will be a considerable letdown for John," says state Sen. Ray Garland (R-Roanoke), a close friend. "The fact that he's apparently ruled out opposing Byrd is incentive for Byrd not to step aside. After 1982, the calendar starts working against John although there's no sense of desperation on his part."

The governor himelf prefers to speak of past political triumphs -- he boasts that his margin of votes in his 1973 lieutenant governor's race and 1977 gubernatorial campaign were the largest in recent state history -- but he concedes the future is uncertain. Contrary to widespread belief, he said, he has not ruled out taking on Byrd, a beloved conservative independent who draws support from the same wealthy businessmen who have been Dalton's key constituency. At the same time, Dalton concedes a race against Byrd could "play into the hands of a liberal Democrat."

"I'm not sure at this point that I want to continue in government as something I'll spend the rest of my life on," sayd Dalton, noting he could make far more money practicing law. "There's hardly a day goes by when somebody doesn't question me on that . . . I really don't know as I'm talking to you today what I'm going to do."

During last year's legislative session, Dalton lobbied for and won an increase in the statewide gasoline tax. This year, the conservative governor's concentration on politics and his determination to hold back from new initiatives have made him largely an invisible force at the Assembly.

"He's been less involved than in any, session I can remember," says long-time political friend Del. Vincent F. Callahan (R-Fairfax). "It's partly because it's his last year and partly because he's accomplished most of what he set out to do."

The legislature's allocation of the state's $201 million surplus is one of the few major issues Dalton has expressed concern about and its fate is being closely monitored by his top financial aide, Secretary of Administration and Finance Charles B. Walker. But the administration's silence on most other key legislative issues has prompted some embarrassing incidents.

A week ago, for instance, a legislative committee heard testimony on a proposal to establish an independent state public utilities department. The bill, which proponents claimed would give consumers more clout in utility rate cases, had been a major plank Dalton's 1977 campaign. Yet the governor sent no one to speak for it and it was overwhelmingly defeated. A few days later, two cabinet secretaries appeared before a different committee to support a minor bill giving the governor the power to appoint the director of the state's game commission.

Dalton says he avoided the utilities department fight because he knew from past experience that the bill would fail. "There is no reason to beat a dead horse," he says.

Others contend the reluctance to fight a losing battle is symptomatic of Dalton's regime. They trace it to the fate that Dalton's adoptive father, Ted, a former state senator and retired federal judge, suffered in losing several statewide political contests to the then-ruling Byrd Machine 30 years ago.

"Ted Dalton was this state's most noble figure and, because he would not bow to orthodoxy and political convention, he was destroyed," says Garland. "That lesson was not lost on his son and John has been reluctant to be bloodied in fights he doesn't think he can win."

While friends say Dalton still brings a briefcase home each night to his upstairs study in the Governor's Mansion, he appears to have more time this year for relaation and for the partisan pursuits he loves best. "He worked so hard his first two or three years," says former press secretary William Royall. "This year he's got the whole thing down to the point where he can enjoy it."

. . . That sense of relaxation has not applied to the press, with whom Dalton still maintains an uneasy, sometimes hostile, relationship. He hasn't held a general press conference since early December and some reporters complain they were refused traditional year-end interviews. Dalton denies he has made himself remote from what is an increasingly aggressive statehouse press corps, and takes exception to what he labels the "inordinate amount of attention" paid by reporters to "some very, very small items."

Dalton singles out as especially irritating stories about his personal expenses at the Mansion. "That has been blown up in headlines all over the state" he says. "The truth of the matter is we've actually cut the mansion by three employes since I've been governor. Nobody pays attention to that. But you spend a couple of hundred dollars for shrimp and that makes headlines."

In the end, as Dalton realizes, historians --not reporters -- will determine the success of his administration. Although he anticipates a favorable judgment, even Dalton allows that stewardship, not creativity, has been his administration's hallmark.

"We haven't tried in these three years to expand Virginia government in lots of additional fields," he says. "I felt it was a time to take cognizance of what we've done and try to improve on what we've done but not get out into vast areas."