A survey released today by Brazilian polling agency Datafolha shows that voter support for ruling party presidential candidate Dilma Rousseff has fallen to a one-month low of 46 percent, down from 49 percent one week ago and 51 percent the week before. Results from the poll, which surveyed 3,180 people and have a 2 percent margin of error, make it more likely that a runoff will take place four weeks after the first round of voting on October 3. A candidate needs at least 50 percent of the valid vote to win outright.

Analysts suggest corruption allegations against the government are turning well-informed middle-class voters away from President Lula’s hand-picked successor. Last week, Erenice Guerra—who replaced Rousseff as Lula’s chief of staff—resigned over allegations that she sought kickbacks for helping businesses secure contracts and state loans for public work projects. Previously, members of Lula’s Partido dos Trabalhadores (PT) were accused of illegally releasing the tax records of opposition candidate José Serra’s daughter.

Serra, of the centrist Partido da Social Democracia Brasileira (PSDB), has tried to use the recent scandals to his advantage, but data from this most recent poll show that his support among voters has remained steady at 28 percent. Rather, voter support for Partido Verde candidate Marina Silva increased 2 percentage points to 16 percent.

Although the recent scandals and slip in Rousseff’s popularity may affect her ability to win in a first round, they are unlikely to affect the final outcome of the election. Data from the new Datafolha poll show Rousseff beating Serra in a second round, 52 to 39 percent.

The latest polls out of Brazil show presidential candidate Dilma Rousseff winning the support of 49 percent of voters polled, with a 20 percentage-point lead over her nearest challenger, former São Paulo governor José Serra, who trails behind with 29 percent. Green Party candidate Marina Silva lagged at 9 percent. A candidate in Brazil needs at least 50 percent to avoid a runoff and these newest results make a first-round win in the October 3 election increasingly likely.

Ms. Rousseff received a major bump in name recognition and popularity after last week’s launch of her national television campaign, which included prime-time ad spots clearly linking her to ever-popular President Luis Inácio Lula da Silva.

An outright win for Rousseff may give the one-time energy minister a mandate for her legislative agenda, which some believe will stay close to Lula’s playbook of a strong state combined with market-friendly practices. Some economic analysts however, say Rousseff could be considering a much bolder policy agenda, including budget cuts to allow for lower interest rates, limits to the growth of public spending and reforms to the tax code.

The Datafolha poll was based on a nationwide sample of 10,948 people and has a margin of error of plus or minus 2 percentage points.