It has been almost six years since Harry Roe Hughes, who had just been installed as the state's 57th governor, stood on the east portico of Maryland's historic Georgian State House here and pronounced his inauguration "a celebration of real change."

Pledging to make independence and integrity the hallmarks of his administration, Hughes -- swept into office partly by the public reaction to the racketeering conviction of former governor Marvin Mandel -- vowed to lead the state based on "what is right, not what is expedient."

At the three-quarter point of his tenure, judging whether Hughes has made good on those promises defies easy analysis even for those who have watched him closely over the years. An intensely private man whose achievements are inextricably tied to the independent General Assembly he helped create, Hughes remains something of an enigma.

History no doubt will show that it was during Hughes' governorship that Maryland began the effort to rescue the national resource of the Chesapeake Bay and applied rigorous standards of merit to gubernatorial appointments that once had more to do with the whimsy of politics.

It will also note that under Hughes, Maryland adopted an aggressive program to halt the carnage caused by drunk drivers, significantly boosted aid to local education, raised its gasoline tax to pay for critically needed road and bridge repairs, and remained solvent and compassionate when other states floundered under a sagging economy and a less-generous national administration.

But what also may remain in the eye of history, some observers suggest, is the nagging sense of lost opportunities that dogs the Hughes administration, the sense that for all his insistence on doing "what is right," Hughes has not led the state in directions it might have gone under someone more forceful or visionary.

"A legislator by trade is an accommodator, a negotiator, a compromiser," said one former aide, recalling an essential facet of Hughes' makeup: his 16 years as a member of the General Assembly. "Harry's not a fighter, he's not a confrontationalist. What Harry is best at is taking somebody else's clear vision and saying 'that's workable,' 'that's doable' or 'that's out of the question.' He's much better at reacting to other people's vision than creating his own."

Whether any of that matters to a public that views Hughes with favor is debatable. Reelected by a landslide in 1982, Hughes has grown in popularity since then. A poll by the University of Maryland Survey Research Center shows that Hughes received good or excellent marks from 54 percent of Maryland residents this past fall, compared with 32 percent in 1981.

Maryland's Constitution limits its governors to two successive terms, and Hughes' second term expires in January 1987. Should he run for the U.S. Senate in 1986, as many politicians expect, he would be a formidable candidate running on a solid record. He gets good, though rarely excellent, notices from a number of disparate quarters.

Welfare advocate Ann Crosson credits Hughes for being "sensitive to the issues of the poor," but she says he could have done more.

Common Cause Director Ricki Wadsworth noted that Hughes "has been good, but not outstanding. He hasn't done a whole lot to promote good government legislation."

Chamber of Commerce spokesman Charles Krautler noted that Hughes' record on business concerns has not always been what the chamber would have liked, "but is getting much better now, there's a consistent record of improvement."

The assessments are much the same within the legislature, whose independence as "the principal policy-making body of government" Hughes vowed to respect during his first inaugural speech.

House Speaker Benjamin L. Cardin, the person who has benefited more than anyone from the long leash Hughes has given the legislature, cites the evolution of a "proper balance" between the General Assembly and the executive as Hughes' premier accomplishment. "The legislature will not allow the governor to dominate again," Cardin said, "and that is good for the people of Maryland."

But there rests one of Hughes' failings, said one legislative leader -- the reluctance to prod a part-time legislature on issues it would not explore by itself. Hughes, said the legislator, "literally waits until problems hit him over the head. The Chesapeake Bay and drunk driving programs , we should have had more of those. We could have had it in the state personnel system, in higher education, in transportation, in prison reform. There are so many areas where we could have had that type of initiative. You don't get those opportunities very often."

"The legislature," added Del. Timothy F. Maloney (D-Prince George's), "has gone full swing from having almost no power in the Mandel era to where we've now entered an era of legislative government in Maryland. We are now involved in executive branch activities. It's dangerous . . . a little bit frightening."

Hughes sees only the positive side of giving the legislature more independence. "I think six years have shown that by working with the legislature and trying to come to a consensus on issues, you are able to accomplish more. That in itself is leadership."

Many of those who have worked beside him agree. Said Benjamin Bialek, the governor's chief legislative aide: "I don't think people realize to what extent the governor makes decisions on merit . . . on what's right for the little guy . . . I can't think of any instance where his caution has hurt the state."

The two areas in which Hughes is most widely accorded high marks are his Chesapeake Bay initiatives of last year and his success in erasing the public memory of what House Majority Leader Donald B. Robertson calls "a rather sordid period in Maryland government" in which politicians went to jail on a regular basis.

The bay package has yet to yield its promised dividends, but on the integrity question, Hughes has already left his mark. His administration has been free of scandal, and appointments solely on the basis of politics have been rare. He has sought aggressively to name blacks and women to positions throughout state government, and he is given high marks for his judicial and regulatory board appointments.

"His enduring legacy will be, with the possible exception of the bay, the restoration of the political mental health of the state," said Attorney General Stephen H. Sachs, a man who calls Hughes "a far better governor than most people, particularly the press, give him credit for being."

But the price of that, said Sachs, "is a shrinking of the sense of possibilities of the office, an aggrandizement of legislative power . . . . In the long run that is not a good thing."

That feeling of underachievement is a common thread running through discussions of Hughes, even by those who view him most favorably.

"He has done very few things I think are wrong," said Del. Nancy Kopp (D-Montgomery), "but he could have done more. I hesitate to say he hasn't had vision, but he hasn't imparted it, he hasn't led. He could have been a great governor, but he won't in retrospect be viewed that way. He will be seen as a good governor."

At times Hughes has shown political courage. He is given credit for resisting the national tax-cutting mood some years ago by standing fast against legislative calls for arbitrary limits on state spending. And Hughes pushed his gasoline tax in an election year, after being rebuffed in 1981.

But there are instances in which Hughes has been faulted for ducking the hard ones. Hughes, said a former aide, has concentrated on "the sexy issue of the day, the political issue of the day" while tending to skirt those that promise little political payoff.

Two examples most often cited are his failure to come to grips with the entrenched problems of the state personnel system and higher education.

It has been two years since a Hughes-appointed task force first recommended a major overhaul of how Maryland rewards its roughly 60,000 nonuniversity employes. The Commission on Compensation and Personnel Policies proposed that the state restructure job classifications, upgrade salaries to make state service more competitive with private industry and junk the system of giving salary increases based solely on longevity.

But the proposals have languished, ostensibly because Hughes wants the commission to incorporate into its proposal the concept of comparable worth, that thorny problem of balancing the value of traditionally female occupations with historically male jobs.

"You'd have to go back and start all over again" if the state did not include comparable worth in the personnel review, argued Hughes. Others say that is a smoke screen, that Hughes simply lacked the resolve to push through expensive and politically difficult recommendations.

The same criticisms are heard in relation to the governor's loss of enthusiasm for reorganizing Maryland's balkanized system of higher education. With too many schools competing for too few dollars and fighting over programs and turf, the need for a new form of governance with some centralized authority is widely recognized.

But not long before the election of 1982, Hughes' commitment flagged. The governor said no one could find the right "model." Others say Hughes was simply unwilling to contend with such sensitive issues as the future of Maryland's historically black institutions.

For all that, Hughes is getting better notices as he nears the end of his term. Like partners in a maturing marriage, he and the legislature have grown accustomed to each other's quirks.

Ask legislators to grade Hughes, and often the answer is B plus. "If he'd managed the office with dynamic energy, he could have been an A governor," said Del. Kopp. "But there are very few A governors."

Ask Harry Hughes to grade himself, and you get this response: "My mother was a schoolteacher and she never let her students grade their own papers."