THE MOST CROWDED race in this fall's city-council election is taking place in an unlikely setting: Dorchester's District Three, where popular four-term incumbent Maureen Feeney is fighting no fewer than five challengers. This profusion of challenges to an incumbent isn't unprecedented, but it is uncommon - especially for someone like Feeney, who in 1999 beat her only opponent by 54 percentage points.

It could simply be a strange convergence of the stars. Or, as former councilor John Nucci suggests, the five candidates might be responding to Feeney's perceived "wandering eye," since she twice ran unsuccessfully for the state senate, in 1997 and 1998. "They might not even be people who think they can win," he says, "but they might think they can be heir apparent if Maureen moves on." It could even be, as Feeney speculates, an unintended result of her efforts to encourage civic participation. (Thanks in part to her work, there are now more than 30 neighborhood associations and crime-watch groups in the district.)

But the major reason so many candidates are running for her seat may be the neighborhood's shifting demographics. Dorchester has changed dramatically over the past decade. "You can't talk about it as one neighborhood," says Northeastern University sociologist Will Holton. "They count about 12 different sub-neighborhoods," including pockets dominated by young professionals, Vietnamese and other Southeast Asians, Latinos, Haitians, and African-Americans, in addition to Irish-Americans, who have long dominated the area.

Indeed, the 2000 Census shows that South Dorchester (in rough terms, the area Feeney represents) shifted from 48 percent white in 1990 to 30 percent white in 2000. (The shift has been even more dramatic over a longer stretch of time: the area was 65 percent white in 1980.) In the last decade, the black population increased from 36 percent to 42 percent; multiracial (a new category introduced last year) and "other" went from two percent to eight percent; the Asian population spiked from three percent to 10 percent; and Latinos stayed the same at 10 percent. "In the city, it's the neighborhood that's changed the most in the past 10 years," says George Pillsbury of Boston Vote, an organization devoted to increasing voter turnout.

New populations have new needs. "Maybe the newer residents are looking for somebody to be their spokesman," says former city councilor Larry DiCara. Former District Three councilor James Byrne, who once employed Feeney as his chief-of-staff, agrees: "It's a far-reaching and very diverse district, so you may have certain candidates who feel they have core constituencies they want to bring to the table."

That's certainly true for Feeney's opponents, who seem to represent every facet of Dorchester's multiple identity. Provided that everyone's signatures are certified (a process the Election Department is currently undertaking), voters will be courted by Mark Juaire, an openly gay Connecticut native who moved to Dorchester eight years ago and became involved in the neighborhood's civic groups; Nathan Cooper, an African-American small-business owner who has been active in the revival of Codman Square; Gerard Paul Brophy, an Irish immigrant and housing advocate who plans to reach out to other Dorchester newcomers; Joseph Ureneck, a liberal activist from the 1960s and '70s; and John Comerford, a perennial conservative candidate.

But make no mistake: the race isn't exactly a multicultural love fest. Two weeks ago - nearly two months before the September 25 primary - an anonymous mailing sharply criticizing Feeney was sent to homes across the district. "It was [making] the inference that I'm on the take," Feeney explains. "There was a picture of a man with a fistful of dollars, and on the other side was a woman counting money. You know - 'Who is Maureen Feeney representing in City Hall?'" The mailing correctly stated that Feeney had accepted money ($14,000) from a number of local businesspeople over the past four years. But, she says, "My response would be, show me a vote anywhere where I supported business over the community. It hasn't happened."

Feeney was upset by the attack, which she describes as uncommonly dirty for Dorchester. Democratic political consultant Susan Tracy was unsurprised, however. Dirty campaigning "happens all the time," she says, though "normally it's in the form of gossip and verbal communication." In Boston, she says, "there's a history of anonymous drops - you don't know which opponent did it, or even if the incumbent did. It's part of what's to be expected." Brophy, Cooper, and Juaire firmly denied involvement in the mailing. (Ureneck declined to discuss the race until his signatures are certified, while Comerford declined any comment.) Says Juaire, "I totally disagree with anything anonymous. If people are trying to make a point, they should put their name on it." He adds, "The information they were trying to get across didn't seem [to be] of any particular concern."

In many ways, the District Three race is a microcosm of Dorchester, as new communities organize and build electoral clout. But as the early mudslinging shows, that can be a contentious process.

LAST THURSDAY at lunchtime, Feeney stood outside Patty's Pantry, a convenience store and to-go luncheonette on Dot Ave. Sweating in the 95 degree heat, she handed out pens and Tootsie Rolls to a stream of construction-worker types who passed in and out. "Hi, I'm Maureen Feeney, nice to see you, hope you'll remember me in September," she said in one breath. Some of them took the pens and nodded. But one turned around and replied, "I will - my cousin used to work for you." When she found out who the cousin was, Feeney said excitedly, "I just saw the baby pictures!" A few minutes later, she got a honk from a passing car. The driver, a rough-and-tumble-looking fiftysomething with a missing tooth, hopped out. "How are you, my darling?" said Feeney. She got him to slap on a Feeney bumper sticker. A few minutes later, it was time to go. "We do quick hits, 20 or 30 minutes," said Feeney. But her intern - a cousin of State Representative Marty Walsh of Dorchester - reminded her that she had stop inside to say hi to Arthur Donovan, the owner of Patty's. "It's my favorite councilor!" he roared when she walked to the back counter. These, clearly, are Maureen Feeney's people.