By Alonso Soto BRASILIA (Reuters) – Brazil’s finance minister waded into the country’s presidential campaign on Thursday, warning that an opposition victory in the October election could push the economy into recession and undo a decade of social gains under the ruling Workers’ Party. The comments by Guido Mantega, which the opposition and some analysts criticized as unbecoming of a sitting finance minister, came on the eve of the release of official data that is expected to show that Brazil, Latin America’s largest economy, is already in recession. Brazil’s once high-flying economy has slowed sharply in the last four years under President Dilma Rousseff, complicating her chances for re-election in October.