HORACIO RODRÍGUEZ LARRETA, a Harvard MBA who wants to be Buenos Aires’s next mayor, has a good story to tell. He is the handpicked candidate of the current mayor, Mauricio Macri, who created a rapid-transit bus network and festooned the city with cycle lanes. The polls say Mr Larreta will win in a run-off on July 19th. Mr Macri hopes that will be a springboard for his own campaign to become Argentina’s next president later this year.

But in Buenos Aires’s shantytowns Mr Larreta’s boasts ring hollow. Electricity is erratic and flooding is frequent; ambulances and the police take hours to arrive. The candidate has not given up. Posters extolling him appear amid the aluminium-and-brick shacks of Villa 31, a slum that borders the posh neighbourhood of Retiro. But traditional campaigning will not suffice in the city’s 56 villas, which collectively house 275,000 people, about a tenth of the population. To win votes in such service-starved neighbourhoods Mr Larreta and his rival, Martín Lousteau, a congressman, will quietly rely on local power brokers called punteros (point people).

Punteros are well-known figures who act as problem-solvers, and occasionally as saviours, for the locals. They run football teams, clinics and soup kitchens. In Villa 31 one fills bags with biscuits for women to take to their imprisoned husbands. During a flood in a villa in San Miguel, a suburb of Buenos Aires, a puntero used a boat to fetch an inhaler for a boy suffering from an asthma attack. Such good deeds are part of a lucrative triangular trade. Punteros deliver the votes of grateful citizens to politicians, who in turn find ways to pay the punteros. The more votes a puntero can mobilise the higher the salary.

Such “clientelism” is not unique to Buenos Aires (it is more entrenched in the suburbs) or to Argentina. But Argentina has done less to fight it than other Latin American countries. The governments of Mexico and Brazil, for example, do a better job of distributing benefits and services as a matter of course rather than in exchange for political support, says Rebecca Weitz-Shapiro, a scholar at Brown University in the United States. “Argentina has been a relative laggard in that respect,” she says.

Some punteros cross the line between exchanging favours and committing electoral fraud. Rodrigo Zarazaga of CIAS, a Jesuit research institute, who wrote a doctoral thesis on clientelism, says that of the 120 punteros he interviewed 22 admitted to stealing the ballots of opposing candidates. A political broker in one poor suburb recalls that by six years old his son had become adept at shuffling around ballots. He would wait until the vote counters “dozed off or something, and then—whoosh!” In Buenos Aires’s mayoral election, which uses electronic voting, that is less likely to happen. Punteros rarely affect the results unless the margin is razor-thin, in part because they cannily gravitate toward the likely winners. But candidates do not like to take chances.

Both Mr Larreta and Mr Lousteau portray themselves as crusaders against clientelism. As mayor, Mr Macri tried to “urbanise” shantytowns by improving municipal services, which would have sidelined the punteros. But many slum-dwellers complain that the programme merely brought eye-catching projects like football pitches and public squares, while leaving untouched such ills as poor drainage, impassable roads and violence. So punteros are in no danger of losing their jobs just yet.