On Wednesday last week she cheated death again. She was meant to be on the private jet that crashed near São Paulo in bad weather, killing Eduardo Campos, the presidential candidate, but she changed her plans at the last minute.

The harrowing experiences have turned the 56-year-old into a frail, slightly hunched woman, often seen with dark circles under her eyes. But her battles with death as well as poverty and illiteracy have also strengthened her iron-like resolve, transforming her into a likely leader of the world’s second-largest emerging market.

Members of the Brazilian Socialist Party (PSB) indicated at the weekend that Ms Silva, Mr Campos’s running mate, will replace him in the presidential campaign, sending Brazilians and foreign investors scrambling to understand her position on everything from welfare to the oil industry. While Mr Campos only had about 10 per cent support in the last polls before he died, Ms Silva has a chance of actually beating President Dilma Rousseff and Aécio Neves from the centrist PSDB party, analysts say.

According to the first poll released since Mr Campos’s death, Ms Silva would get 47 per cent of the vote in the second round, compared with 43 per cent for Ms Rousseff – a technical tie given the poll’s 2 percentage point margin of error.

“The most dangerous candidate for Dilma has always been Marina,” says Christopher Garman of Eurasia Group, adding that she managed to get nearly 20 per cent of the vote when she ran for the Green Party in 2010 with little funding or television time. Her popularity on the back of this cuts Ms Rousseff’s hopes of winning the election outright in the first round with 50 per cent of the votes.

Ms Silva’s fight to combat deforestation and protect indigenous communities has won her international prizes and popularity among Brazil’s intellectual elite and creative circles. “Marina sees the possibility of an alternative Brazil,” wrote Fernando Meirelles, director of films such as City of God and The Constant Gardener, in the preface to her biography in 2010. To the dismay of the ruling PT party, Ms Silva was even chosen to carry the Olympic flag in the London 2012 opening ceremony.

However, she has struggled to reconcile her ideals with politics. She served as environment minister under Luiz Inácio Lula da Silva, the former president, from 2003 to 2008. Disillusioned, she left the PT to join the Green Party but then quit in 2011. She only joined forces with Mr Campos last year after she failed to set up her own party, the Rede Sustentabilidade (Sustainable Network).

In a television interview last year, she gave the clearest signs yet of her position: she is against Brazil’s controversial Belo Monte dam, she sees the country’s fast-growing oil industry as a “necessary evil” and she certainly has no patience for the types of ranchers who killed her friend.

On the other hand, she has shown support for the country’s biofuel ethanol industry, she welcomes greater technology investments by farmers and wants to cut their transport costs with better infrastructure.

On the economy, she has expressed opposition to the growing power of Chinese state companies in Brazil and also defended the three pillars of macroeconomic stability established in the late 1990s: inflation targeting, a floating exchange rate and maintenance of a primary fiscal surplus.

“The problem is that the agenda of Brazil is no longer the same one . . . now we need microeconomic reforms,” says Carlos Melo, political scientist at the Insper business school in São Paulo.

However, part of Ms Silva’s appeal is that she does not talk about new policies but rather a new way of doing politics – an idea that could win over many of the younger disenchanted Brazilians who took to the streets in protest last year against everything from corruption to poor public services.

As a staunch evangelical Christian who once considered becoming a nun, she also has the support of the country’s fast-growing evangelical community.

The biggest unknown, though, is whether Ms Silva will be able to win over the country’s poor and new middle classes who are traditionally loyal PT voters. Her personal history certainly qualifies her for their sympathy. After the death of her mother she took on work as a maid and struggled to get into university, where her political career began.

While Mr Lula da Silva’s similar rags to riches story means it is difficult for her to fulfil this role in the electoral space, there are growing signs that his popularity is no longer enough to protect his protégée, Ms Rousseff. The president was booed again on Sunday during Mr Campos’s funeral.

However, if the past week in Brazil has shown anything it is that “when it comes to politics, anything can happen”, says Insper’s Mr Melo.