BRASILIA, Dhu-AlQa'dah 17, 1435, Sep 12, 2014, SPA -- City, Dhu-AlQa'dah 17, 1435, Sep 12, 2014, SPA Brazilian President Dilma Rousseff has narrowed the lead of her top challenger, Marina Silva, to one percentage point in a potential runoff vote expected to follow the Oct. 5 first-round election, an opinion poll by pollster Ibope showed on Friday, Reuters reported. In a runoff, Silva has 43 percent support to 42 percent for Rousseff, said Ibope, which polled more than 2,000 people. The gap represents a statistical tie because it is within the survey's margin of error. Silva had a seven-point lead in last week's Ibope poll. The survey was the latest evidence that Rousseff had recovered from Silva's dramatic surge earlier this month and that her strategy of criticizing the popular environmentalist is paying off. Analysts said Silva, the widely favored contender just over a week ago, has hit her ceiling and the incumbent's more powerful political machine and media exposure have kicked in. If Silva, Rousseff or any other candidate fail to win a majority of votes on Oct. 5, the top two finishers will face each other on Oct. 26. -- SPA 20:03 LOCAL TIME 17:03 GMT www.spa.gov.sa/1272125