Marina Silva has been formally named as the Brazilian Socialist Party’s new presidential candidate.

Environmental campaigner Marina Silva, 56, replaces the late Eduardo Campos, who was killed in a plane crash last week.

Marina Silva was Eduardo Campos’s running mate and served as environment minister.

She is seen as a leading challenger to President Dilma Rousseff, who’s seeking re-election in the October 5 poll.

PSB President Roberto Amaral told a news conference Marina Silva had been chosen unanimously.

Congressman Beto Albuquerque was named the party’s new vice presidential candidate.

Marina Silva will test President Dilma Rousseff’s status as favorite to win October’s election and make this a much more interesting process than it looked like being barely a week ago.

Marina Silva has been formally named as the Brazilian Socialist Party’s new presidential candidate (photo AP)

In the last presidential election, standing as the Green candidate, Marina Silva polled a credible 20% of the vote and is already a recognizable and much-admired figure across this continent-sized nation.

The first test of public opinion after Eduardo Campos’s death suggested Marina Silva could surpass the main opposition PSDB candidate Aecio Neves in the first round and beat current President Dilma Rousseff in the second, although both outcomes were within the poll’s margin of error.

However, analysts caution that, with the strong emotional reaction to last week’s events, a bounce in the polls was inevitable and the picture could change substantially.

A devout evangelical Christian who overcame poverty, Marina Silva only learnt to read and write when she was 16.

Correspondents say she appeals mostly to young voters who are unhappy with the Brazilian political establishment.

On Sunday, more than 100,000 people in Brazil paid their last respects to the late presidential candidate, Eduardo Campos, a former governor and rising political star.

They attended a funeral Mass and filled the streets of the city of Recife to follow the passage of his coffin.

Eduardo Campos’s jet crashed on August 13 in bad weather in the port city Santos, near Sao Paulo, killing six other people. Investigators are still trying to establish the exact causes of the accident.

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