Brazil’s incumbent president Dilma Rousseff has gained back some ground among voters and is tied with challenger Marina Silva for a second round vote, according to a new poll.  The poll from the Datafolha institute shows the president and Ms. Silva technically tied with 43% and 47% support, respectively. For a first round vote, Ms. Rousseff leads by a margin of 36% to 33%. Support for third place challenger Aécio Neves rose one percentage point from the previous poll. Ms. Rousseff, of the Workers’ Party has benefitted recently from campaign attacks on Ms. Silva for her alleged ties to local banking interests and opposition to robust development of Brazil’s offshore oil areas. Ms. Silva has denied those allegations. Brazil is scheduled to hold a first round presidential election on Oct. 5. If no candidate wins more than 50% of the valid vote, the country will hold a runoff election.   The latest poll was taken among 10,500 respondents nationwide and has a margin of error of two percentage points.