Edmond F. Rovner was in a hotel lobby in Japan in June 1973 on a routine trade mission for Gov. Marvin Mandel, when he opened a letter from home. "The dogcatcher has picked up Brandy," it said, then added: "The governor just vetoed your bill."

Rovner remembers thinking the dog had better luck, and that it was time to resign his post as Maryland's secretary of economic and community development.

Four years earlier, after his work on behalf of Montgomery County Democrats helped win him a post as Mandel's chief of staff, Rovner's future in state politics had seemed assured. But two months after his return from Japan he walked out, disillusioned by internal power plays and by his growing isolation in the administration.

Now, after an eight-year hiatus from partisan politics, the 51-year-old Rovner is back in Montgomery County, playing the role of political sage and troubleshooter as a key aide to County Executive Charles W. Gilchrist at the start of a year in which Gilchrist is expected to seek reelection.

Rovner arrived in his new post in February, when Gilchrist was struggling to overcome a growing controversy over the handling of an appointment to the county's Department of Liquor Control.

At the time, Gilchrist said he hired Rovner in order to "increase the dialogue between county government and the people of this county." What that meant, other officials said privately, is that Rovner's mission was to help smooth over the liquor controversy and to shore up Gilchrist's public image.

Observers differ in their assessments of how well he has succeeded. Nearly a year after his appointment, Rovner has become Gilchrist's closest aide. He has helped coordinate a series of initiatives by the county executive on social issues, including a major program of aid for the working poor, an effort to combat incidents of racial and religious harassment and an unusual attack on the county school board's actions on school closings.

Some officials and observers claim Rovner's effectiveness has been hampered by what they see as his overbearing personality, but Gilchrist disagrees.

"He's worked out superbly. He brings extensive experience to almost everything that comes up," Gilchrist said. " Rovner has a strong personality, but I think that is a definite plus."

When Rovner was appointed to the $44,000-a-year position, party regulars who had questioned the logic of Gilchrist's earlier appointments were relieved that a politically experienced man finally was being brought to the executive's inner circle.

"Most of the party people reacted with absolute delight when Ed was brought in . . . the best move Charlie ever made," said one county Democratic official, who added that many county Democrats believed Gerard Evans and Thomas B. Stone Jr., then Gilchrist's two top aides, lacked experience.

Supporters say Rovner has been an invaluable addition to Gilchrist's staff, that he is an excellent strategist with a fine political mind and a quick wit. Former Mandel press secretary Frank DeFilippo described him as the "ideas man" in the Mandel administration and said he has broad and useful contacts on local, state and federal levels. Stone praises Rovner's knack for "looking at the larger picture of an idea and pulling it together."

"Ed tends to be more of a generalist. Details and specifics are not his strong points," said one associate. "He has a real talent for putting things in perspective. It's a positive influence because we needed things like that so badly here."

On the other hand, detractors, both past and present, painted a far different portrait, calling him a "loose cannon"--erratic, temperamental and high strung. Rovner also has been described as a political gypsy--someone who rapidly loses interest in a job and quickly moves to another--and as an aide who was never very influential with Mandel.

"Sometimes he strikes people as being a little too mercurial and very blunt, but in the administration he's the closest to Gilchrist on everything," said county spokesman Charles Maier.

Sitting in his office, where autographed photos of Great Society and New Frontier Democrats are prominently displayed, Rovner said he sees himself as the "old government hand" in the Gilchrist administration.

"I've functioned in the county a long time and know a lot of people in the community. I'm a sounding board to make suggestions for Gilchrist to sharpen his teeth on when an idea is being considered."

Rovner's connection with politics began in his childhood. He was born in the Bronx in 1929, "a few weeks before the stock market crashed," he said. His father, David, drove a cab. Clara, his mother, worked as a part-time cashier. While Rovner was growing up, Roosevelt was president, La Guardia was mayor of New York City, and the politically active Clara usually dragged her son along to local Liberal Party meetings.

Rovner graduated from Columbia University Law School in 1952 and came to Washington as an attorney for the National Labor Relations Board. From 1954 to 1965, he worked as the associate general counsel and then as the director of civic affairs for the 300,000-member International Electrical, Radio and Machine Workers Union. Rovner's experience in that job, says Montgomery County Attorney Paul McGuckian, has been invaluable as the county works out a collective bargaining and binding arbitration agreement with the county's 722-member police force.

While he worked for the union, Rovner also served a term as president of the Washington chapter of Americans for Democratic Action and was active in Montgomery County politics. He was campaign manager for the highly successful liberal Montgomery Democratic Action Group in 1966.

Rovner had joined the staff of Rep. Jonathan Bingham (D-N.Y.) in 1965 as an administrative assistant. Said Bingham recently: "Ed knew who the people were who could get things done," crediting Rovner with the idea of expanding the Voting Rights Act to include party caucuses and primaries.

On New Year's Eve, 1969, Rovner was informed that Mandel, then speaker of the house of the Maryland General Assembly, had enough votes to become governor and wanted him on the staff.

"It was a bittersweet experience. It gave me a chance to operate on a large scale, but by the same token, it was an atmosphere that was abusive, frustrating . . . the capacity was there to do great things, but it was being debased by people who were out for personal interests," said Rovner of his Mandel days.

"Ed fit in not very well with Mandel. There were conflicts of personality and style. He was never one of the Mandel inner circle and that bothered him," said longtime Maryland political observer Peter Jay, now publisher of The Record in Havre De Grace. "But his relationship with the press was good. The problem was they felt he was too close to the press."

Rovner is credited with streamlining the executive branch of the state government while Mandel's chief of staff, but, according to another high Mandel aide, Rovner "had a damned time in Annapolis. Mandel was interested in him at first, but cooled on him."

According to DeFilippo, "Ed did not like to fight. He would come in, present his idea and get very upset if a bad idea won. It got very scrappy, and Ed couldn't deal with the pettiness and the bickering."

Rovner's job as chief of staff ended in 1970, when Mandel appointed him secretary of economic and community development. After leaving Annapolis in 1973, he spent five years on the staff of the National Governors' Association, then worked briefly as congressional liaison for the federal Office of Surface Mining.

In 1979, he became staff director and counsel for the House Subcommittee on Consumer Protection and Finance. A minor stroke sidelined him for six weeks, but he returned to that post later in the year and remained there until the position was abolished by reorganization in February of this year.

Rovner, whose wife is a staff writer for The Washington Post, says his eventual goal in life is to teach college-level political science. But for now, he says he enjoys working with county-level government, where he finds the administration not prone to the "competitiveness" that he says stifled ideas among Mandel staffers.

"Gilchrist is not a lone ranger. He talks and listens to a lot of people. It's not a hierarchical system," said county spokesman Maier.

One insider says that Rovner's real advances have been in improving Gilchrist's public image, saying that Rovner "picks out what's good and amplifies it."

But Rovner's relations with the local press have not always been smooth. In April 1981, he and editors of The Washington Star had a sharp dispute over complaints he had about that paper's coverage of the Liquor Department controversy. More recently, a public flap developed over his refusal to invite a Montgomery Journal reporter to a Capitol Hill birthday party for Gilchrist.

Rovner dismisses both incidents as unimportant and says he is satisfied with his relationship with the press.

For the 1982 campaign, Rovner said his role would probably not be on the front lines, but behind the scenes. He said he does not want to be campaign manager for the Gilchrist reelection effort.

DeFilippo, Rovner's closest friend in the Mandel days, says there is nothing unusual about this. "He's a career staff man, the classic second banana. He'd rather operate in the background."