Brazil's great leftist experiment is under the microscope in the first major elections since the working class president, Luiz Inacio Lula da Silva, was elected in 2002.
In the middle of Lula's unprecedented term, a mayoral vote has taken on the appearance of a federal election, not just a state one, and a crucial test of his governance so far.
But according to opinion polls, the ruling Workers' Party candidate and incumbent Marta Suplicy is set to lose to Jose Serra of the Brazilian Social Democrat Party in the key mayoral election in Sao Paulo, where a quarter of the electorate live.
If Suplicy were to be defeated it would be a significant setback to Lula's declared hopes of being re-elected president in 2006.
The final mayoral vote will take place on October 31 and the results known in minutes thanks to Brazil's electronic voting system.
President Lula's political future
hinges on Sao Paulo's result
The usually reliable opinion polls put Serra between 10% and 14% ahead.
But Suplicy is fighting hard.
In her tenure she has cut the cost of urban travel - essential in a city of nearly 20 million - with an innovative and effective one-ticket scheme to allow passengers to pay once for as many bus trips as they like in any two-hour slot.
For many, that could amount to savings equivalent to their monthly grocery bill.
It is a relatively small but significant step for millions of the urban poor who survive on less than a dollar a day in a country infamous for inequality and corruption in high office.
All about image
By tackling and breaking the city's bus mafia, Suplicy says she was subjected to various death threats. It is the message her image-makers are driving at with the billboard slogan "A Woman of Courage".
And image is all-important in a country that has a small
newspaper-reading culture and low literacy rates.
Elections are largely played out on television that, by law, dedicates a peak-time "electoral hour" every night for months before the vote.
"You need to understand that I am not God, I am just one person. I have worked hard and will continue to work hard to enlarge my projects because it is not easy to create and implement them"
Sao Paulo mayor Marta Suplicy
Serra's campaign managers have chosen "now it's Serra", a
poke-in-the-eye for Lula who used "now it's Lula" as his successful campaign slogan two years earlier.
He was the government candidate Lula defeated in the 2002 presidential election.
Serra was the internationally celebrated health minister in the
previous administration who broke convention and licensed generic medicines to combat HIV which were on average 40% cheaper than those sold by multinational pharmaceutical companies.
It is a model since copied globally. He also banned TV cigarette advertising. The battleground that Serra is certain to win on is health.
Bland v blonde
But where he is regarded as a bland man-in-a-suit, blonde-haired red-suited Suplicy has sparkle and a past TV career as a sexologist.
Her daily election promotion includes eulogies from various rappers, singers, club owners and stylists.
"She is conscientious and very elegant," says singer Paulo Lima. "She understands that fashion is culture and this can only bring benefits," stylist Alexandre Herchcovitch chimes in.
Former sexologist Suplicy's (L)
fortunes are closely tied to Lula
But the mayor recently lost her image guru - Brazil's top PR agent - and that is not helpful to her campaign.
Duda Mendonca, the publicist credited with winning the election for Lula at his forth attempt, was arrested for taking part in an illegal cock-fight last week on 21 October.
Mendonca is the most powerful image-maker in Latin America and had also brought Argentina's Carlos Menem back to power in the mid-90s.
"The whole of Brazil knows that this is my hobby," said an unrepentant Mendonca, but he was promptly suspended from Suplicy's campaign.
Back in the real world and in the battle of the buses, Serra is
proposing to steal Suplicy's thunder - and idea - and expand the one-ticket scheme to the whole state.
"The population needs to move more rapidly in the whole state. Because of this I have an eye on the future and not on short-term political factors, " he said.
"I have an eye on the future and not on short-term political factors"
Mayoral candidate Jose Serra
In her latest rally, Suplicy told the voters: "You need to
understand that I am not God, I am just one person. I have worked hard and will continue to work hard to enlarge my projects because it is not easy to create and implement them, like the one ticket."
President Lula is keeping an arm's length from the contest after being fined $17,000 for breaking electoral law and pitching for Suplicy during the opening of a new motorway - Brazilian law forbids presidents using government projects for political ends.
But his future could depend on the result. It will either indicate that he is on the road to serve until 2010 or that Brazil's first left administration could be strangled at birth within the next two years.