BUSINESS-FRIENDLY LEFTIST
Campos, the leader of the Brazilian Socialist Party and a former governor of the northeastern state of Pernambuco, was running as a market-friendly leftist and had strong support from many banks and industrial groups.
His running mate Silva placed a strong third in the 2010 presidential election, but her pro-environment agenda means that many in Brazil's powerful agribusiness sector distrust her.
Silva, who was not on the plane that crashed, did not immediately make any statements following Campos' death.
Brazil's main stock index lost as much as 2 percent following initial reports that Campos was on the crashed plane, but later regained ground and was down a little more than 1 percent in afternoon trade. The currency also fell sharply on news of Campos' death but later bounced back.
The entry of Silva into the race could increase the odds of Rousseff facing a runoff, Brown Brothers Harriman said in a note to clients.
"She is very well known and arguably has a closer electoral base to (Rousseff)," the bank said in the note.
On Tuesday night, Campos was in Rio de Janeiro for an interview with Brazil's most-watched nightly news program. Several pundits praised his performance as confident and authoritative, and said he might rise in polls as a result.
Campos was a protege of popular former President Luiz Inacio Lula da Silva before breaking with the ruling Workers' Party in preparation for his presidential run last year.
"Surely he would have had an important role in Brazil's future. Brazil needs leaders like him, with the ability to understand the situation and not store up hatred or animosity. Eduardo was like that," said Fernando Henrique Cardoso, another former president and a member of Neves' party.