Leading opposition presidential candidates Aecio Neves and Eduardo Campos have gained ground early in this year’s election campaign, while support for incumbent president Dilma Rousseff has held steady, according to a poll released Thursday by the Ibope opinion research institute. The poll, sponsored by the Globo television network, showed support for Ms. Rousseff unchanged from a previous survey in June at 38%, while support for Mr. Neves and Mr. Campos rose one percentage point each to 23% and 9% respectively. The poll showed that in a runoff election, support for Ms. Rousseff totaled 42% versus 36% for Mr. Neves. Against Mr. Campos, Ms. Rousseff would win by a difference of 44% to 32%. Under Brazil’s election rules, a runoff election is held if no candidate gets more than 50% of the vote in a first round, scheduled for October 5. The latest poll was taken among 2506 respondents between August 3 and August 6, and has a margin of error of 2 percentage points.