Marina Silva has quit Brazil’s ruling party in what is being widely seen as the start of her bid for the country’s presidency in 2010 under a Green Party banner.

Silva previously resigned as environment minister in 2008, saying that “growing resistance … in important sectors of the government and society” made it impossible for her to protect the Amazon (see: Concern after Brazil loses environment minister – May 15, 2008)

“I am now in talks with the Green Party in this period of transition,” says Silva. Jose Maria Cardoso da Silva, of Conservation International, told Reuters that this would lead to “a real debate about sustainable development”.

On the on the Brazil Political Comment blog, John Fitzpatrick notes:

The fact that Silva, a former environment minister, has no chance of winning is less important than the effect of her announcement This has stirred life into what looked like a two-horse race between President Luiz Inacio Lula da Silva´s candidate, Dilma Rousseff, and the likely PSDB candidate, Jose Serra, the governor of São Paulo. It also increases the chances of other candidates, like Ciro Gomes of the PSB, standing and means there is now a greater chance of the election going into a second round.