AUGUST is a tragic month in Brazilian presidential politics. Sixty years ago Getúlio Vargas, a populist dictator turned democrat, committed suicide while in office. In 1976 Juscelino Kubitschek, who had built Brasília, the country’s Utopian capital, was killed in a car crash. This year, the month claimed its latest victim. On the morning of August 13th Eduardo Campos, leader of the Brazilian Socialist Party (PSB) and one of President Dilma Rousseff’s two main rivals in an election this October, perished when his chartered aeroplane crashed in the port city of Santos, 60km south-east of São Paulo. The aircraft, a popular Cessna 560XL executive jet, was reportedly in perfect working order when it took off at 9:21am from Rio de Janeiro, where the candidate had given a series of television interviews on Brazil’s biggest television network the night before. Bad weather meant that landing at the Guarujá airstrip in Santos, where Mr Campos was making a campaign stop, had to be aborted. Soon afterwards, eye witnesses reported hearing an explosion and seeing the Cessna plummet ablaze into several apartments building and a gym. The cause of the explosion, which also claimed the lives of two pilots and four of Mr Campos’s campaign staff, remains murky; there was unconfirmed speculation of a mid-air collision with a helicopter.

Eulogies immediately began streaming in from across the political spectrum. Ms Rousseff, with whom Mr Campos had served in the government of her predecessor, Luiz Inácio Lula da Silva, before breaking ranks to pursue his own ambitions, declared three days of national mourning and suspended her campaign for the period. So did Aécio Neves, candidate of the centre-right Party of Brazilian Social Democracy (PSDB), who tweeted of “an irreparable and incomprehensible loss”.

The 49-year-old Mr Campos was widely seen as one of the few bright spots among the younger batch of Brazilian political leaders. As governor of the north-eastern state of Pernambuco from 2007 until April this year, he married market-friendly measures with poverty-reduction schemes. The poor loved him. But businessmen and financiers would come out of meetings with the socialist leader similarly besotted.

Mr Campos was on his way to São Paulo to address just such a crowd (as well as your correspondent) when he died. As conference organisers broke news of the tragedy, the besuited audience gasped in disbelief, then fell into stunned silence. Soon, though, shock turned to commotion. Traders, analysts and pundits began frenetically revising election scenarios with clients, many of whom were also in attendance. Brazil’s main stockmarket index dropped by 2% before rebounding. The real also dipped briefly against the dollar.

The initial selloff can be explained in part by general shock. But it also signalled a changing electoral dynamic. The markets appear at first to have interpreted Mr Campos’s demise as shortening the odds of a second Rousseff administration—and thus four more years of her Workers’ Party (PT), lambasted by many in the private sector as interventionist and anti-business. The latest polls put support for Mr Campos at just under one-tenth of the electorate, roughly 30 points behind Ms Rousseff and 14 points behind Mr Neves. With Mr Campos out of the race, this reasoning goes, the prospects of Ms Rousseff’s winning more than half of valid votes cast in the first round, thus avoiding a tight run-off with Mr Neves, have brightened.

The subsequent rebound, says Tony Volpon of Nomura, a broker, suggests that markets remembered about Mr Campos’s running mate, Marina Silva. The PSB, which now has ten days to pick a new candidate, is almost certain to plump for the former senator and Lula’s environment minister.

If she does run, as she is widely expected to, Ms Silva could fracture the political debate, long polarised between the PT and PSDB. She is “the PT’s biggest nightmare”, notes Mr Volpon, who likens her hard-scrabble upbringing in the poor north makes to a female version of Lula, revered by many Brazilians for his biography, as much as his successful cash-transfer programmes. That makes Ms Silva hard to attack as a heartless neo-liberal, a charge levelled against Mr Neves.

In 2010 Ms Silva took Brazil by storm with her presidential bid, and in particular her astute use of social networks. This let her come from nowhere to end in close third, with 20m votes. Psephologists put her core support at 12-14%, higher than Mr Campos’s. Her idealism and probity goes down well with young, urban voters fed up with politics as usual. Nearly two-thirds of Brazilians aged 16 to 24 remain undecided. Cajoling them to polling booths, as she is likely to if she runs, makes a second round all but inevitable, says João Castro Neves of Eurasia Group, a consultancy.

Both Mr Neves and the president boast bigger war chests and more extensive party structures. In the coming weeks Ms Silva can count on a sympathy boost in the polls, though whether this will be big and lasting enough to threaten Mr Neves’s position as Ms Rousseff’s principal challenger will not become clear until the first post-accident polls, probably late next week. Several pollsters have cancelled planned fieldwork to let Brazilians digest their loss.

Visibly shaken by the loss of a friend and ally, Ms Silva has not yet declared her intentions. She has not shied away from controversial decisions in the past. Joining forces with Mr Campos, chummy with agribusiness, was one such for an avowed environmentalist (a trait which puts off some Brazilian businessmen). Pulling out of the race would be another. For now Ms Silva is grieving. So is the Brazilian nation.