Behind its stately Georgian exterior, the Maryland governor's mansion harbors a treasure trove of political turmoil.

In the days of Spiro T. Agnew, citizens raged over the governor's exclusive parties for the "$1,000 Club," a clique of big Republican contributors. Marvin Mandel's mansion troubles peaked when his first wife refused to vacate the premises during their separation, forcing the governor to repair to the Hilton Hotel down the street--followed by television cameras. After Mandel's untimely departure came the uproar over missing state furniture, liquor, silver, china and bric-a-brac. And then came Harry Hughes, promising to elevate the 120-year-old mansion above politics, above furor, above its sometimes tawdry past.

But history has reasserted itself: turmoil has returned. ("You'd think the damned place was haunted," observed Sen. Victor Crawford of Montgomery County.) It appears that the Hugheses are mixing mansion life with, of all things, politics.

The governor and First Lady Patricia Hughes have hosted a series of Monday night cocktail suppers for legislators, two dozen at a time, inviting each to bring along six constituents from the home district for a "social evening" of drinks, music, finger food and chitchat. ("No shop talk," Pat Hughes admonishes the pols as they pass through the receiving line.)

Legislators, who tend to invite their most valued precinct workers to these evenings, consider them "your basic smart election-year politics," as Del. Casper Taylor (D-Allegany) put it. And few criticize the dinners since, in Taylor's words, "I'd do the same thing myself." Even Pat Hughes is quick to acknowledge: "We're certainly aware of the fact that a social evening is a lubricant."

But none dares call it politics in Hughes' staff offices in the State House across the street. The mere suggestion by legislators that the state-funded dinners have an election year flavor prompts Hughes' press secretary, Lou Panos, to draw in his breath and expound for several minutes about the public-spirited nature of the evenings at "the house that belongs to the people."

These protestations have riled many politicians, and while the Hughes-era hubbub is fairly tame by Maryland standards, it is typical of the way the governor's pious and apolitical style has at times strained relations with the General Assembly.

The matter came to a head last week when a freshman Baltimore delegate attempted to embarrass Hughes by inviting as one of his six guests a convicted burglar now serving a 12-year sentence at Brockbridge Correctional Facility in Jessup. Del. David Shapiro then issued pious-toned statements of his own, expressing hope that Hughes would grant Robert E. Wechsler, 51, a furlough for the evening, and hear the inmate's story of Maryland's troubled prison system from "the other side of the wall."

"Look, we're all politicians here," Shapiro said. "To me, what he's doing is so unbelievably political. It's Harry Hughes-style drycleaned politics, but it's politics and I just wanted to highlight that fact."

Most legislators shrugged off Shapiro's stunt, but Hughes took it so seriously that he opened his latest press conference with a statement on the Wechsler affair, giving it priority over such pending legislative issues as clean air, interest rates and taxes.

The governor read aloud a letter from his prisons chief to Shapiro, denying Wechsler's furlough request, pointing out that the inmate is now serving time for nighttime burglary, "which as you know is a very serious crime." Hughes also brought with him Wechsler's rap sheet, which dates back to 1948, and noted that it is literally as long as his arm. "This gentleman does have a rather long record, by the way," Hughes said.

Hughes went on to reassert that the mansion dinners are "not political functions. If they were political functions, I'd invite who I wanted," rather than allowing legislators to do the inviting.

The governor called Shapiro's caper "rude," saying that some of the other invited legislators and guests had expressed concern to him about dining with a convict. This led to a round of snickers from veteran pols over the irony of it all, since two recent occupants of the historic mansion are convicted felons--Mandel, who was convicted of fraud and racketeering in 1977, and Agnew, who pleaded no contest to a charge of income tax evasion in 1973.

Beyond causing a momentary furor, the Monday night dinners reflect the way Hughes has used the mansion for the last three years to advance his own brand of politics. They also highlight the role of his wife, Pat, in shaping his social style, much as political aides have shaped his official style.

Pat Hughes keeps a detailed guest list of every group she has entertained at the mansion, starting with the Jan. 17, 1979, inaugural buffet. She notes that the list crosscuts almost every constituency, geographical region and interest group in the state. "I call this my report card," she said. The first lady also sends an aide to each of her husband's staff meetings to learn of political problems that she can help solve with some social "lubrication."

"She is constantly watching him to make sure he stays as dignified as she wants to see him stay," Cas Taylor said of the first lady. "She perceives dignity as a political virtue. She gives me the impression that if she saw Harry with a big cigar in his mouth, she'd walk over there and yank it out."

At the Monday night dinners, Hughes stands under a portrait of George Washington to receive guests in the newly renovated federal room. He is flanked by the first lady and the first dog, a shaggy cocker named Beau who sports a needlepoint collar in the official state colors--red, black and gold. A state photographer shoots a portrait of each guest with the first family and the governor personally autographs them all ("no machine signatures," the first lady observes) before they are mailed to the folks back home.

While some may call it "strictly social," it does have its political benefits, according to legislators. Several of them said their guests offered afterward to work for the governor's reelection.

"Look, people love that stuff," said Crawford. "Even the Montgomery County holier than thou jaded set--they're impressed." photo: Gov. and Mrs. Harry Hughes and Beau in the Federal Reception Room, where they greet guests at the Maryland Governor's Mansion. (By Gary A. Cameron-TWP)