SAO PAULO — WHEN Luiza Erundina de Souza won the Sao Paulo mayoral election for the Workers' Party in 1988, she astonished and frightened many Paulistanos.Catapulted into the mayor's seat by a voter backlash at traditional politicians, she was suddenly pelted with questions about her radical political views, forged during years of mobilizing the city's homeless to invade empty lots. Asked if she believed in armed struggle, Ms. de Souza stunned TV viewers by saying that she did if the majority wanted change and a minority tried to impede it. Three years later, the former social worker still believes in favoring the poor, a majority in Sao Paulo. But her answer has softened. "She says she believes in peaceful change," notes a spokesman. The soft-spoken socialist has learned by doing. She intended to freeze bus fares to make transportation more affordable, but the city council refused to subsidize the bus system. Now she has worked out a scheme with private contractors to pay them on the basis of the distances their bus fleets cover, instead of the number of passengers they carry, and to encourage expanded service throughout the city's 580 square miles, almost double New York City's 304 square miles. "In the next two months, there should be a thousand new buses in the streets," says the spokesman. "In the last 15 years there has been no increase in the [total] bus fleet, and the population grew 3.5 million." At rush hour, with young messenger boys hanging off the back doors, Sao Paulo buses carry an average of 12 passengers per square meter, well above the ideal of seven, according to the Metropolitan Collective Transport Company. The daughter of a saddle maker, de Souza initially met with urban prejudices against rural northeastern migrants who, like herself, were drawn to Sao Paulo's lights. But criticism eased as she worked together with business and state government. De Souza has embarked on a series of programs for the poor, all emphasizing self-help and dignity instead of charity and dependence. Still, taxi driver Antonio Martins is not impressed. "My opinion is very bad because she encourages people to invade property. A lot of sidewalk vendors have invaded Sao Paulo, and they don't pay taxes; they dirty the city and steal. They are good-for-nothings from the north, where she is from," he says. "The city is full of holes and she halted the public works of the previous administration." A recent opinion poll of the mostly low-income users of city services, however, found that more than 50 percent said services had improved during de Souza's administration. Ratings on a scale of 1 to 10 covering a variety of specific services were never lower than seven. More than anything, the mayor's experience reflects the valuable lessons that can be learned in the practice of democracy, a system that is new to Brazil since a military dictatorship left power in 1985. "[You] have to change people's idea of authority as absolute power and be very clear about the limits and responsibilities of government. And be very clear about the limits of local, municipal power," she says. "It's not enough to be a good administrator. You have to be a good politician, too, to relate to society and other government levels, to solve the city's problems."