The latest polls ahead of a runoff presidential vote Sunday showed a tight race, with incumbent Dilma Rousseff still holding a slight lead over challenger Aécio Neves. Major polling institutes Datafolha and Ibope continued to show an advantage for Ms. Rousseff, of the Workers’s Party, but support for Mr. Neves, of the opposition Social Democratic Party, was showing a last-minute advance. A poll from Datafolha projected Ms. Rousseff with 52% of the valid vote versus 48% for Mr. Neves. At the same time, an Ibope poll estimated Ms. Rousseff with support from 53%, versus 47% for Mr. Neves. Both institutes, however, showed that support for Mr. Neves had grown from previous surveys, while support for Ms. Rousseff stayed unchanged. Meanwhile, a poll from the Sensus insitute showed Mr. Neves leading by 52% to 48% and a poll from the MDA institute showed the two candidates tied with 50% each. The candidacy of Mr. Neves, who held a lead in polls early in the race, appeared to gain a boost ahead of the election this week with a well-evaluated performance in televised debates against Ms. Rousseff. Ms. Rousseff’s campaign was also hurt by last-minute allegations published in the Veja weekly news magazine that her government had conncetions to alleged corruption at state-run oil company Petrobras. Ms. Rousseff denied the allegations. Ms. Rousseff won a first-round election against Mr. Neves on Oct. 5 by a tally of 42% to 34%.