The four men who huddled together in a downtown Baltimore office last spring represented the essence of Mayor William Donald Schaefer's political strengths.

One was a lawyer, another a businessman. The third was a black community leader and the fourth a nationally known developer.

They had a grand plan -- to support Schaefer's gubernatorial ambitions -- and to that end, they conceived a fund-raising extravaganza scheduled to take place tonight in Baltimore. The gala is expected to raise at least $1 million -- the largest amount of money ever raised in a single event for a single candidate in Maryland.

If that happens, its only near-competitor for the fund-raising honor would be the Four Star Salute held for then-Gov. Marvin Mandel and three other candidates in 1973. That raised $917,000, and was held before a $1,000 limit was placed on the size of contributions that can be made to any one candidate.

It was the idea of Harborplace developer James W. Rouse to pull together a grand salute to Schaefer, a 63-year-old Democrat, on the occasion of his 30 years in public service. Rouse and the other three men at the meeting -- lawyer Robert S. Hillman, businessman James W. Smith and Samuel T. Daniels, the executive director of the city's Council for Equal Business Opportunity -- are a brain trust that Schaefer has drawn on during his 14 years as mayor as he has wooed businesses, welcomed developers who rebuilt the city's urban core and remained popular with a majority black population.

After their meeting, the four organized a small luncheon at a luxury downtown hotel and later a larger wine and cheese party at a local jazz club, inviting people they knew they could count on to sell tickets to the fund-raiser.

They are too cautious to predict they will actually raise the $1 million. But earlier this week, Hillman was confident enough to say that Schaefer will probably "crack" the Mandel record, establishing a hefty campaign war chest for what everyone except Schaefer is publicly saying will be his 1986 race for governor.

Schaefer has told officials around the state that he is running, even though he will not confirm that to the press. During the last several months, he has made tentative campaign forays into areas outside Baltimore and received a warm response in every case, except in Prince George's County.

He is still bitter about the hostile reception he received at a private meeting with black Democrats in Prince George's, who characterized him as "arrogant" and "condescending." And he blames County Executive Parris Glendening, who organized the meeting and was once touted as a possible candidate for lieutenant governor on Schaefer's ticket, for the problem.

Glendening said he will be at tonight's gala, where he will join thousands of other politicians and monied supporters. A poll published this week in the Baltimore Sun showed that Schaefer enjoys a 5-to-1 lead over his most vigorous campaign opponent, Attorney General Stephen H. Sachs.

In an interview earlier this week, Schaefer said that lopsided poll results can be a mixed blessing. "If I would slip in a poll one-tenth of a point, the headlines would say, 'Schaefer's popularity eroding,' " he said.

Yet while Schaefer frets, his lieutenants say they've had no trouble selling fund-raiser tickets. They say their effort illustrates that the mayor is perceived as a doer who rebuilt Baltimore, as well as a charmer, as evidenced by his dancing with singer Marie Osmond at the City Fair last weekend. That combination, his supporters say, has brought him statewide support.

From his downtown Baltimore high-rise office, Hillman fielded phone calls from people such as Allen Quille, a businessman who is a member of Baltimore's black political old guard. Quille called to report that he had sold 196 tickets at $100 apiece to the Convention Center event. Several hundred people also are expected to pay $500 a ticket tonight for the privilege of shaking the mayor's hand at a smaller reception at the downtown Omni Hotel.

"At the outset, nobody really expected an event this large," Smith said.

The signs were there at the start, though. Nathan Landow, a national Democratic fund-raiser and Montgomery County developer, said he agreed to sell $100,000 worth of tickets because "the mayor's a pro." Laurel Mayor Robert DiPietro said he sold 10 to 20 tickets easily. "I haven't made the first phone call," he said.

"It's been a very easy sell," Hillman said. No freebies were handed out to elected officials or others, he said.

Some politicians have chosen to be more circumspect. U.S. Rep. Steny Hoyer, for example. didn't sell any tickets but said he plans to attend. Prince George's state Sen. Thomas V. Mike Miller Jr., a Schaefer supporter, said he bought a ticket but was not asked to sell one. The ticket-selling network, he said, included only heavyweights.

Schaefer's potential opponents are conceding that tonight's event will not soon be matched in terms of the psychological and fiscal boost it will provide a Schaefer campaign.

Sachs' campaign manager Blair Lee IV said this week that he is hoping to blunt the impact of the publicity Schaefer will receive by soliciting 10,000 contributions of $5 apiece through the mail in coming weeks. A letter mailed to 2,700 potential Sachs contributors this week said that the money will pay for an early Sachs "TV blitz" of 100 campaign commercials that will air the week of Oct. 20.

"The focus that the mayor's event will draw to the governor's race creates a window of opportunity," Lee said.

House Speaker Benjamin L. Cardin, a third Democratic gubernatorial contender, could not be reached for comment.

For Schaefer, the organizing has just begun. When tonight's gold dust has settled, Smith said, planning will get started for the next event. Smith, who ran U.S. Sen. Paul Sarbanes' 1982 campaign, estimated that Schaefer will need at least $2 million to run and win statewide.

Schaefer is not expected to announce his intentions formally until after the 1986 General Assembly session has ended. "I think there's an expectation we'll catch [Sachs] in the spring," the mayor said.