The deceased Brazilian presidential candidate Eduardo Campos, 49, was a former governor of the northeastern state of Pernambuco and belongs to a traditional family from the Brazilian political establishment.
In the latest opinion polls Campos had 10% support from likely voters, according to a survey released on July 22 by polling firm Ibope ahead of the October 5 first-round election.
President Dilma Rousseff, who is standing for a second four-year term, leads the race with 38% support, while social democrat Aecio Neves has 22%, the poll found. The presidential campaign officially opens on August 19.
Campos had been traveling to Sao Paulo, the Brazilian financial hub, to film a campaign-related TV segment with his running mate, ecologist Marina Silva, Globo TV reported. Silva was not aboard the plane, reports said.
Campos, who was married with five children, had been running on a platform of change after 20 years of government by Rousseff's Workers' Party (PT) and Neves's PSDB.
He had served as science and technology minister from 2004 to 2005 under Rousseff's mentor and predecessor Lula da Silva.
Lawmakers from Campos's PSB party expressed their shock on Twitter.
It is with great sadness that I received the news of the tragedy involving Eduardo Campos. I'm very upset, representative Julio Delgado tweeted.
We lost our greatest leader. I'm devastated, said colleague Beto Albuquerque.
However when the mourning is over, and the campaign officially begins, there will be surprises in the electoral scenario because of Marina Silva, who is expected to become the head of the Socialist presidential ticket.
Originally from an Amazon rubber tappers family, a leading member of Lula da Silva's Workers Party, Senator and later minister, she abandoned the party disenchanted with the government's environment and indigenous peoples policies. In 2010 she run for the presidential office with the Green party and against all odds and opinion polls, garnered 19.5% of the vote.
She later organized a sustainable network with environmentalists, minority groups and others who support a sustainable economy as opposed to an extraction, wasteful economy. Silva's organization was not accepted as a political party and was forced into a strategic alliance with Campos, as vice-president hopeful.
Marina is considered a formidable campaigner, and is a big magnet for many disenchanted voters from the ruling party, which has become too 'orthodox and distant from its original charter'.
In other words a formidable challenge for Dilma Rousseff, more even than Campos.