The telephone rang recently in the office of prominent Baltimore banker Howard Skaggs, and a surprise caller was at the other end. "All he said was, 'I'm going to have a few people in for dinner and would you come?' " Skaggs recalled.

The caller was Gov. Harry Hughes, a man whom Skaggs, once a leading fundraiser for former governor Marvin Mandel, says he does not know well. Skaggs accepted the invitation, at first a little baffled. Then it all began to make sense: "You start thinking: Now why was I invited down to the governor's mansion ? Oh yeah. Next year's election year. Oh ho!"

In typically understated style, Harry Hughes has started campaigning for reelection, even sending out feelers for a 1982 running mate to replace Lieutenant Gov. Sam Bogley, the administration's odd man out.

Hughes has not declared his intentions officially, remaining so quiet about them that rumors have surfaced that he might not run. But in the last two weeks, Hughes and his wife Pat have unofficially launched his campaign at a series of intimate dinners with 40 of Maryland's wealthiest and best-connected citizens and their spouses.

Two dinners have been held, two more are scheduled this month, and the scenario at each is the same. The chitchat goes on for more than an hour through cocktails and into dinner -- swordfish, asparagus and wine, at one session -- before anyone mentions the obvious. Even then, the selling is very soft. Hughes modestly lists his accomplishments, and then one of his top political financiers -- either developer James Rouse or Crown Central Petroleum board chairman Henry A. Rosenberg Jr. -- makes the point a little more directly: Hughes is running for reelection and would like some help.

"It probably was the most low-key pitch ever made in the history of politics," said Secretary of State Fred Wineland, one of the guests who remembers the hard-sell styles of past governors. "If you didn't know an election was coming up, you'd never know it was a suggestion that you raise funds for the governor's reelection."

With election day a year from today, the Hughes campaign is advancing on several fronts in a field relatively clear of challengers. No major Democratic opponent has yet surfaced, although some observers believe Hughes is vulnerable, and only one Republican, Anne Arundel County Executive Robert Pascal, has begun mobilizing. That could change, however, if Hughes fares badly in the coming General Assembly session or if he is unable to shake the image of a do-nothing governor that some attribute to his subdued style.

As Hughes' effort gets under way, the contrasts with the 1977 darkhorse days of "Harry Who?" are legion. Then he was the ignored underdog, his campaign run by two friends operating out of a small hotel room. Now he has the power of incumbency -- the money, the visibility, the people it can lure -- and he is beginning to use it.

A small group of intimates, including key statehouse aides John O'Brien and Joe Coale and advertising executive Hal Donofrio, have met several times to discuss campaign timing, guest lists for the dinners, fundraising and the working theme of the reelection effort: "restoration of integrity in goverment." Within a week or two, Coale is to leave his governnment post and move to Baltimore to set up Hughes' first 1982 campaign office.

Hughes, who for his first two years as governor stayed close to the statehouse, recently has packed his schedule with small-town parades, crab feasts and bull roasts, shaking hands with voters from the Western Maryland mountains to the Eastern Shore.

He is to meet later this month with a national pollster who soon will be surveying Hughes' strength and the vote-getting power of several potential Bogley replacements. While Hughes intimates say a running mate will not be selected until next spring, the governor already has had preliminary talks with a few prominent Democrats about teaming up in 1982.

Baltimore County Executive Donald Hutchinson is at the top of Hughes' list largely because of his popularity in the vote-rich Baltimore area, where Hughes has shown some vulnerability. Hutchinson, who is officially running for his own reelection, is known to be interested. Other Democrats often mentioned are House Speaker Benjamin L. Cardin of Baltimore, who apparently prefers, however, to remain in his powerful legislative role, and Montgomery County Executive Charles Gilchrist.

Although a Harry Hughes for Governor 1982 committee was formed in August 1980, the serious fundraising began only two weeks ago with the mansion dinners. Paid for by the committee, the dinners are intended to raise seed money, but not for a shoestring operation as in 1978. This time, the goal is $1 million, half of it to be raised by the beginning of the year.

The guest lists for the dinners show that Hughes the incumbent is trying to expand his campaign inner circle beyond that of Hughes the longshot. Some guests -- such as retired engineer Charles B. Allen, businessman Allen Quill and attorney John Howard, all from the Baltimore area -- are old friends or 1978 loyalists. But others have never prominently supported Hughes before, and some are better identified with Hughes' past opponents and predecessors, including Mandel, Spiro Agnew and Blair Lee III.

Conspicuous among the guests are several ardent supporters of Baltimore Mayor William Donald Schaefer, including Rosenberg, cochairman of the mayor's huge fundraiser last June. Their presence indicates that Hughes is seeking to smooth strained relations with the popular Schaefer, who already is being wooed by Pascal and whose support is considered a prerequisite to a heavy turnout in Baltimore.

The new financiers Hughes hopes to recruit through the dinners include Skaggs, wealthy scrap metal businessman I.D. Schapiro, national Democratic party fundraiser Nathan Landow, former Agnew associate Tilton Dobbin and Baltimore attorney M. Peter Moser. Some, such as Landow and Moser, Hughes' 1982 campaign treasurer, have already signed on. Others, including Skaggs and Schapiro, remain uncommitted. "No commitment was asked, none was given," said Skaggs.

But while Hughes was careful to avoid directly asking his guests for money or support -- "We're not that crass," one insider said -- he has since pressed the point a little further. Within a few days of the dinners several guests received personal notes from Hughes that said, as one businessman recalled: "I know that you're interested in good government for the state and I hope that you will respond."