What do a blond sexologist, a failed presidential nominee and a man accused of laundering millions of dollars through a Swiss bank account have in common?

In the colorful world of Brazilian politics, they are the leading candidates for mayor of South America's largest city.

One of them already is the mayor, Marta Suplicy, a sex expert by training who is seeking a second four-year term. Another, Paulo Maluf, has served as mayor twice, once in the 1990s, during which time he allegedly siphoned off tens of millions of dollars in public funds to a private account in Europe.

Of the three major candidates, only Jose Serra has never actually held the post, but not for want of trying: He ran and lost in 1996. Two years ago, he also got trounced in a bid for president, defeated in a landslide by Luiz Inacio Lula da Silva, a former lathe operator and union leader who is backing Suplicy for reelection.

But the fortunes of politicians in Brazil are ever-changing, and polls show that the somewhat starchy, gray-suited Serra now has his best shot at leading his native city, a post often regarded as a springboard to higher office.

The race in Sao Paulo is the most publicized contest in this country's municipal elections, scheduled for Sunday. Voters are to choose mayors in all of Brazil's more than 5,500 cities, from remote towns in the Amazon to megalopolises such as Rio de Janeiro.

Analysts are paying close attention to the elections as an indicator of public sentiment about Lula, who is nearly halfway through his term as president. With the economy showing signs of life after a dismal year, Lula's approval ratings have begun to bounce back, and some pundits predict that his left-leaning Workers' Party, or PT, could make significant gains outside its traditional strongholds in major cities.

"These elections are critical . . . because they'll determine the grass-roots base of support that parties can count upon in coming elections," said Christopher Garman, an analyst with Tendencias, a consultancy here in Sao Paulo. If Lula's comrades and allied parties can win control of more city halls, "they'll create a political base of support in interior parts of states where voters have never voted PT."

The biggest plum remains Sao Paulo, whose mayor commands a national profile in Brazil much the way as the mayor of New York does in the United States. As a sign of its importance, the mayoral contest here is setting records for campaign spending.

This sprawling city, which is celebrating the 450th anniversary of its founding, is Brazil's industrial and financial capital, home to gleaming skyscrapers, expensive boutiques and a private helicopter fleet second in size only to New York's. It is sophisticated and cosmopolitan, a place where high-end sushi restaurants and art galleries are packed with successful professionals and established socialites.

But below its shiny surface are profound problems. More than 1 million residents live in squalid slums, often without basic sanitation and other services. Unemployment verges on 20 percent. Violence is pervasive: Last year, the city recorded more than 4,000 murders.

Lula's Workers' Party, with its emphasis on improving the lot of the common man, was born here -- but gets no free ride.

"If you look at Sao Paulo's electorate, it tends to be more conservative than the national electorate," Garman said. "In the presidential election [of 2002], Lula beat Jose Serra in the city of Sao Paulo by 120,000 votes, which is less than 1 percentage point, whereas he beat Serra by a very large margin in the rest of the country. He barely won Sao Paulo when he had almost a landslide on the national level."

Lula has been vocal in his support of Suplicy, a longtime activist in the Workers' Party despite a personal background of wealth and privilege.

Admirers of the 59-year-old incumbent call her a vibrant, indefatigable champion of the downtrodden who has toiled hard to improve health and education in poorer parts of the city. Last year, to ease Sao Paulo's nightmarish traffic, Suplicy initiated a series of massive transportation projects, but construction work has only worsened congestion, critics say.

At a forum this month, Suplicy appealed to voters to give her the chance to finish what she began.

"To be mayor of this city for eight years is the chance of a lifetime," she said. "I was born here. I have a passion for this city. I understand this city."

But many Paulistas are unconvinced. Detractors are turned off by what they describe as the arrogant demeanor of a woman better known for her haute couture suits, her divorce from an influential senator and the daily TV program on sexuality she hosted in the 1980s.

"I'm poor. I'm not rich," said Jose de Freitas, a retiree. "What has she done for me?"

Similar criticisms of aloofness hang over de Freitas's preferred candidate, Serra, 62, of the Brazilian Social Democracy Party.

Brainy and academic, the former national health minister is campaigning under the slogan "The Mayor of the People." Yet many recall a gaffe from his 2002 presidential campaign. On a visit to one of Rio's shantytowns, where functioning sewer systems and consistent electricity are luxuries, Serra brushed aside a resident who insisted on speaking to him and told her to send him a fax.

Serra has released few specific policy proposals, but polls put him and Suplicy in a dead heat at the top. In a second-round runoff -- an increasingly likely outcome -- Serra is thought to be the heavy favorite.

In third place in the polls and slipping after a strong start is Maluf, the Brazilian Progressive Party candidate. A respectable showing could give him considerable clout in the second round as his rivals court his support.

Maluf, 73, has served not only as mayor but also as governor of the state of Sao Paulo. He is seasoned and flamboyant, but widely regarded as a crooked politician. His own supporters boast: "He steals, but he gets things done."