In second term, Dukakis keeps style plain, simple.

Precisely at 8 a.m. a dark blue compact sedan pulls up in front of a gabled-roof, 21/2-story brick duplex home in Brookline. A pensive-looking, short but well-proportioned man in a light seersucker suit and carrying an attache case strides down the driveway past well-manicured shrubs and gets in the back seat, partly occupied already by a stack of files.

Gov. Michael S. Dukakis thus begins a day that will include a drive to southeastern Massachusetts for a closed-door huddle with area state legislators, a briefing on Bristol County's efforts to curb drunk driving, a visit to the site of a planned new county jail and house of correction, and a session with chamber of commerce officials from around the region.

''We're going to be doing a lot more of this,'' explains the governor, occasionally looking up from leafing through a stack of memos, letters, and reports as the car moves along.

Unlike many state chief executives, including most of his predecessors in the Massachusetts State House, Governor Dukakis has no intention of becoming tied to his office and perhaps in the process losing touch with the people out around the state.

''Just being able occasionally to sit for a couple of hours with real, live people who are on the scene and getting a sense of things from them is very valuable,'' he explains.

Later in the year, the governor says, he hopes to be able to ''take three to five days going out and just quietly sitting with people and listening to what they have to say on a particular subject.''

During his first term (1975-78) and early last year, so-called gubernatorial ''town meetings'' in various communities around the state were regularly scheduled. But not any more. ''They're a good idea, and we may try them again, but having them every two weeks, month in and month out, doesn't seem to work that well, and they tend to be repetitive,'' Dukakis says.

In August, seeking an alternative way to bring state government closer to citizens outside the Boston area, the governor, his cabinet, and top aides shifted executive branch operations from Boston to western Massachusetts for three days.

In addition, Dukakis has been holding ''small meetings on their turf'' with state legislators, drumming up support for several of his key proposals.

About an hour after leaving his Brookline home, the governor arrives in the southeastern Massachusetts city of Fall River and meets with 10 area legislators. He urges them to support a measure that would set up a new means of financing new roads, bridges, water systems, and sewer lines.

Later he motors to New Bedford to tell a gathering of southeastern business leaders that passage of the legislation is vital to economic growth in the area and throughout the state.

By 2 p.m. Dukakis is back in his State House office in Boston. There he keeps several appointments, holds two brief press conferences, has an interview with an NBC-TV reporter, swears in a state appeals court judge, and holds a late-afternoon meeting with key aides.

Although the Dukakis schedule varies widely, he says he tries to spend a part of several days a week out of the office. This is not always possible when the legislature is in session, he acknowledges.

Dukakis, whose use of public transportation received national attention at the beginning of his first term, still rides Boston's subway system. ''I'm on board two or three days a week,'' he notes, adding that it gives him ''a chance to meet folks I otherwise would not meet.''

He also uses commuting time to meet with staff members. ''Sometimes, when it's necessary to talk with someone and there doesn't seem to be time to do it in the office, I find it useful to have the individual swing by, and we ride in to work together.'' Catherine Dunham, special assistant for human resources, rode with him on the drive to Fall River, updating Dukakis on her work.

With all this activity, the governor still makes room virtually every day for what he calls ''family time'' - usually the dinner hour. He also tries to reserve Sundays for family activity.

''This is very important to me, even when I have to be out in the evening,'' he explains. On those few evenings when he does not have to go some place after dinner, reports and papers brought home from the office take up considerable time.

To help keep in shape and relax, Dukakis is out jogging, ''usually late at night,'' several times a week.

A high school and college athlete, he recalls an incident when playing squash with Carl Levin, an ''old friend'' and classmate at both Swarthmore College and Harvard Law School who now is a Democratic US senator from Michigan.

''He almost destroyed my political career when my face got in the way of his racquet.''

Dukakis says he knows ''what it's like to lose,'' having been unseated in the 1978 Democratic primary after his first term, only to turn the tables on his toppler, Edward J. King, four years later.

But the Bay State's ''new breed'' governor, who was among those considered by Democratic presidential nominee Walter Mondale as a possible vice-presidential choice, says he doesn't think a Mondale loss to President Reagan this November is inevitable.

He describes former Vice-President Mondale as ''warm, friendly, effervescent, and a very funny guy,'' but concedes he does not come off that way on television.

Dukakis began his political career in 1958 with election as a town meeting member in Brookline. In the early 1960s he gained prominence in Massachusetts as a leader of an activist group bent on reforming the state Democratic Party. That effort succeeded, and reforms instituted since have broadened and opened up the party's power structure.

Prior to wresting the Bay State governorship from Republican hands in November 1974, Dukakis had served eight years in the Massachusetts House of Representatives, from which he voluntarily retired in 1970 to run, unsuccessfully, for lieutenant governor.

Later, he became nationally known as moderator of ''The Advocates,'' an issue-oriented weekly program on public television. Dukakis spent three years ( 1981-83) between gubernatorial terms on the faculty of Harvard University's John F. Kennedy School of Government. ''It gave him an opportunity to ''look back and see what we might have done differently,'' he explains.

One thing he is handling differently in his new term is legislative relations. His first term was marked by confrontation with a legislature controlled by his own party. This time around Dukakis's relations with leaders of the State House and Senate have been vastly improved, even though the same politicians are in charge of those chambers.

The governor lists among what he considers major accomplishments during his tenure reduction in welfare rolls to the lowest point in the past 11 years and an unemployment rate that is the lowest among all the industrial states and consistently below the national average.

''We are doing things here that could be a model nationally,'' he declares, citing his administration's ''employment and training program'' under which welfare mothers have acquired skills and steady jobs.

He views having ''a sympathetic administration'' as essential in dealing with various social problems and says that ''sharing these successes with other parts of the country ... is what providing real national leadership is all about.''

A political liberal and proud of it, Dukakis makes clear that this in no way means he is soft on such issues as law enforcement. He calls legislation he is pushing for a tougher sentencing policy ''a progressive and liberal bill.''

Underscoring his strong commitment to reducing drunk driving, Dukakis and his wife, in each of the past two springs, have stopped in at several high school proms to urge the young people to keep their big night liquor-free.

Unlike many high-ranking public figures, Dukakis has no speech writer. He says he feels he does his best using notes rather than working from a prepared text, although conceding this might make it a bit more difficult for reporters covering his speeches.

'I've got a wonderful job and a great opportunity to do things that count and help make our state better,'' Dukakis declares. ''What would make things complete would be to have an administration in the White House that I could work with, one that shares a lot of my goals and values.

''We're doing pretty well here in Massachusetts on our own,'' he adds.

With more than two years left in his current term, Dukakis already is thinking about what would be his third four-year stint on Beacon Hill. ''I think I would like to do it again,'' he says, but adds that before a decision is made he will discuss it with his family.

Although unwilling to speculate beyond the governorship, Dukakis isn't closing off any political options, including perhaps a federal cabinet post.

But the governor, whose ''Mr. Clean'' political image has remained intact throughout his career in public office, doesn't plan to return to the practice of law. An eventual professorial role is more to his liking.