By Anthony Boadle BRASILIA (Reuters) – Brazilian presidential hopeful Aecio Neves is heading into Sunday’s election with a slight edge over environmentalist Marina Silva in the race to advance to an expected runoff against the incumbent, three new polls showed on Saturday. But on the eve of the vote, it remained unclear who President Dilma Rousseff’s adversary would be in a likely second-round vote later in the month, since the gap between Neves and Silva was within the polls’ margin of error, setting the stage for Brazil’s tightest election in decades. …
