UPDATE 1-Brazil's Silva launches bid, threatens Rousseff re-election
(Adds political context, background on Silva)
By Anthony Boadle
BRASILIA Aug 20 (Reuters) - Environmentalist Marina Silva officially launched a bid for president on Wednesday, upending Brazil's October elections and threatening the ruling Workers' Party's 12-year hold on power.
Silva, until now a vice-presidential candidate for the Brazilian Socialist Party, accepted its nomination to top the ticket after candidate Eduardo Campos, a former governor and rising political star, was killed in a plane crash last week.
Viewed as an outsider with no links to traditional elites, Silva is a former environment minister whose ironclad environmental and religious beliefs prompt critics to call her inflexible but supporters to praise her as Brazil's most principled politician.
Silva, a rubber tapper in her youth who was illiterate until adolescence, appeals mostly to young voters disgusted with Brazil's political establishment.
But she is also embraced by Brazil's large evangelical Christian community and has proven, in a 2010 bid for the presidency with the Green Party, to be an attractive candidate for independent voters seeking an alternative to the Workers' Party and its main opposition, the business-friendly Brazilian Social Democracy Party (PSDB).
An opinion poll on Monday showed Silva, who has vowed to find common ground between her activist ideals and investor-friendly economic policies, tied in second place with the PSDB's Aecio Neves for the Oct. 5 election.
The vote is expected to go to a runoff, at which point Silva or Neves, whomever finishes ahead, enjoys growing odds of defeating President Dilma Rousseff, who has overseen four years of lackluster growth in Brazil's previously booming economy. Continuación...