Three years ago a group of moderate Republicans and Democrats came begging retired Alexandria mayor Charles Beatley to return to city politics. They wanted him to run against a powerful incumbent whose name had come to be associated with an 'ole boy style of city politics the moderates found distasteful.

The moderates reasoned that Beatley, a popular three-term Democratic mayor, was the only one in the city who could take on Frank Mann, of the Mann's potato chip fortune, a Democrat-turned-independent who had spent years in Alexandria politics. The moderates found their man in Beatley who campaigned vigorously and beat Mann by a margin of 2 to 1. "I was the one they came to," says Beatley, "because I was the only one in the city who could do it."

Today, Vice Mayor Robert Calhoun, a Republican, will announce he will oppose Beatley's attempt for a fifth term at a series of station-wagon stops across the city. Calhoun, a Washington lawyer, is the first Republican to run for the office since Reconstruction, and his candidacy will test the growing clout of Alexandria's Republican Party.

The race also will break old alliances and pit against one another moderates of both parties who have cooperated with each other more than they have fought. In Alexandria, a city where national politics usually do not make it across the river, and where the Democrats have ruled for decades, the partisan swords have been drawn for the city's May elections.

Unlike Virginia's recent gubernatorial race, the two mayoral candidates are as dissimilar as the tortoise and the hare.

Beatley, 65, a twinkly-eyed, ruddy-faced retired airline pilot whose relaxed governing style and placid exterior belie a quick mind with a memory for facts and figures, chairs the biweekly council meetings and public hearings with a quiet, rocklike calm. Active in city affairs since 1951, he often has played a conciliator's role as mayor. Beatley seldom interrupts a speaker, and is adamant about making sure everyone gets a chance to speak.

Recently retired from United Airlines, he has made the mayorship virtually a full-time job, taking time out periodically for the glider plane soaring center he runs at his farm near Warrenton.

Beatley takes credit for having guided the city through trying years of rapid growth, and having fought for much of what today gives the city its unique character. It was during his administrations, he says, that the city changed from a sleepy Southern town run by an old guard of bankers and utilities to a modern, efficient city.

"I think its going to be a partisan race," Beatley says. "In the best of all possible worlds, small city politics should be nonpartisan. But I think that this time will be different in Alexandria -- I'm concerned about the Republican administration. There are a lot of good people, but a lot of wild people, too, and frankly, I don't have much confidence in their economics."

Calhoun, 44, a sharp, fast-talking, often witty transportation lawyer with a Connecticut Avenue firm, is a moderate Republican. He has been on the Alexandria council since 1976, and in 1979 polled the highest number of votes, winning the post of vice mayor. At council meetings Calhoun bounds up and down from his seat frequently, often retreating to a side room where he can be seen wheeling, dealing and debating.

When he has wielded the gavel in Beatley's absence, Calhoun has proved impatient with long speeches, (except when they are his own, his detractors like to point out), and aggressively moves meetings at a brisk pace. Supporters and critics alike say that the brashness may come across as slightly imperious. "If Bob could learn a little humility, he'd have it made," said one top city official recently.

In a city government where issues often are batted around for months and where concensus has been the rule for the last decade, many Alexandrians say the race will center not on Metro, not the waterfront, not the Torpedo Factory or even U.S. budget cuts, though that is sure to be discussed. The race will come down to the three Ps: personality, popularity and partisanship.

In the last four days Calhoun has hammered away, albeit decorously, at Beatley's style, or what he perceives as a lack of it. His comments and those of other Republicans indicate that their strategy will be to pay homage to Beatley, the man, while challenging Beatley, the politician, as an official who has lost his effectiveness. A man well-intentioned but no longer equipped to really command a city government Calhoun likes to refer to as being directionless.

"We spend too much time deciding things," says Calhoun, a reference to the biweekly Tuesday night council meetings, which frequently last six hours, and Saturday public hearings, which run about 10 hours later, often with docketed business uncompleted. "I object to running the thing like a family dinner, with everyone sitting around saying whatever pops into his or her head. There's a lack of discipline. I don't like that. When discussion starts to ramble, I tap the gavel." The city council, says Calhoun, "has to set policy, not just react."

Beatley, who has proven himself a clever campaigner, and who has been actually campaigning for a month already, says he will run on his record, and indications are he will play the Republican budget cut blues for all they're worth.

"The proof of the pudding is in the results," he says, saying it was his leadership and foresight that played a large part in establishment of lucrative city landmarks like the Torpedo Factory, the recently approved waterfront agreement, the National Airport plan, and a newly established city park.

Though Beatley has often said that the ideal small city government is nonpartisan, he has begun reluctantly to bring up national politics, which usually do not figure in local elections, but could cast a pall this year. "These are some good people, but there are some wild people up there, too," is how he describes the current Republican administration.

These days Alexandria's Republican Party is anything but wild. In fact, the rise of the Republicans in the city may be the biggest change of all in the city, Metro and waterfront settlements notwithstanding.

In the last election, for the first time, the Republican Party had candidates for each of the six seats on council, and when the results were in, the three top vote getters were the Republican candidates. The party's city committee has swelled from a handful to more than 100 in just over a decade. By all accounts, though Virginia voters do not register by party, Alexandria's 47,000 registered voters split right down the middle, though the city's black vote still is solidly Democratic.