When Alexandria's mayoral campaign began early this month, most city politicians predicted a quiet race that would center on such standard issues as the size of the city budget, the level of taxation and the quality of social services.

In the last three weeks, however, the candidates in the race have proved these observers wrong. Instead of discussing issues, they are busy lashing out at each other -- a startling phenomenon in a city that considers polite politics part of its birthright.

At their most recent encounter, former mayor Charles E. Beatley told a noontime audience that "a flavor of something... we don't like" had crept into City Hall since his opponent, Frank E. Mann, was elected mayor three years ago.

Mann returned the shot moments later when he said that Beatley, a former airline pilot, had an unrealistic view of city government and was getting his political advice "from on high." To vote for Beatley in the general election on May 1 would be "to vote in haste and repent in leisure," Mann said, as the audience gasped.

"We are not used to such campaigns around here," said one observer, who appeared to be both appalled and titillated by the unexpectedly rough campaign styles. "We usually do things in a more subdued manner," he said.

Both Mann, who is running as an independent, and Beatley, a Democrat, told the noontime audience at a Kiwanis Club lunch last week that there were no differences between them on the issues. Each said he believes in lowering the property tax rate, increasing government efficiency, and in providing adequate social services to needy Alexandrians. What they do differ on is style.

Mann, 58, a former owner of the company that makes Mann's potato chips and now a director of the First Commonwealth Savings and Loan Association, was one of the strongest defenders of former commonwealth's attorney William L. Cowhig, who was a central figure in the city's recent bingo and illegal gambling investigations. Cowhig was indicted on three charges, acquitted on two and resigned when the third felony charge was dropped.

Beatley, who has criticized Mann's support of Cowhig, claimed in an interview that illegal games would not have been allowed to flourish had he been mayor. Mann later responded that "the illegal nature of the games cannot be controlled by the mayor," even if they had been known at the time.

Mann, who first served as mayor from 1961 to 1967, was elected to another three-year term in 1976. The post, which pays $8,500 annually, has traditionally been treated as a part-time job, although Mann says he spends more than 40 hours a week working for the city.

One of Mann's main jobs as mayor is presiding over meetings of the City Council, a group of which he is an equal member, according to state law.

Some of Mann's six fellow council members, however, feel that the mayor considers himself more than equal and sometimes treats them in a highhanded manner when he is running their meetings.

In a surprisingly strong statement made at a dinner in her honor Saturday night, Alexandria's Vice Mayor Nora Lamborne said, "The years [with Mann as mayor] have been hell... The mayor is not a god or superior to every other council member."

Lamborne added that, "A crisis has developed in the council-city manager form of government" because of Mann's personality. She then endorsed Beatley, saying "God help this city if you are defeated."

Yesterday Mann could not be reached for comment on Lamborne's statements. In the past, Mann has acknowledged sharp differences with Lamborne, saying that she and other "civic activists" are not used to the hard-nosed approach needed to manage a city government that spends $250,000 daily.

Beatley, who served as mayor from 1967 to 1976, says that in a city with as many active citizen groups as Alexandria, everyone should get to "speak his fill."

Mann has also thrust himself into situations that have drawn criticism from Beatley's supporters. For one thing, Mann defended a business partner who did not pay taxes on valuable waterfront property for five years. In addition, Mann bought 100 shares of stock in the Alexandria Mariners baseball team, which uses a newly renovated city park, Mann's share represents less than 5 per cent of the total ownership, thus meeting the requirements of the state's conflict of interest laws.

Most recently, Mann offered to sell the city an apartment complex he owns, although no specific need for those units was ever stated by city officials.

Mann has defended all these actions as both legal and appropriate.

"Frank is acting the same way he has always acted, but the city has changed since he was in office the first time," said one city hall official.

That change involves the decline in influence of the small group of businessmen who once dominated Alexandria public life. Cowhig is a member of that group, as is his uncle-by-marriage, City Council member Nicholas A. Colasanto, who was defeated in a bid for a fifth term in the Democratic primary election on March 6.

Beatley, on the other hand, has been aligned throughout his public career with the civic association members who gained a majority on the council with the 1970 elections.

Virtually all of the 16 candidates running for the six council seats are classed by political observers as being "civic association types" rather than having Mann's orientation toward business.

Mann, a witty and charming man in private conversation, was expected to be the more aggressive of the candidates. What surprised some members of the Kiwanis Club last week was that Beatley, the pleasant ex-pilot who once spent 32 minutes speaking on the subject of taxes when he had been asked to speak for a minute, has come out swinging.

About 17,000 of the city's 43,000 eligible voters are expected to go to the polls on May 1. But if the campaign continues at its present pace, many politicians would not be surprised at a much larger turnout.