ISTO É magazine published the results of a survey by the Sensus polling company, which showed Ms. Rousseff gaining 37.3% of support, followed by 22.5% for Ms. Silva and 20.6% for Mr. Neves. The poll has a 2.2% margin for error which makes it a technical tie.

Brazilian Election Prediction Polls Released

Brazilian Election: Runoff predictions

Under Brazilian election rules the top two candidates must contest a runoff if no candidate gets more than 50% of first round votes. If necessary a runoff will be held on October 26.

According to the survey, Ms. Rousseff of the Workers Party would win a runoff against Ms. Silva 44% to 37.6%. The incumbent president would beat Mr. Neves 45.8% to 36.9%.

The 2014 presidential election took a major twist when Socialist Party candidate Eduardo Campos died in a plane crash on August 13.

Brazilian Election: The rise and fall of Marina Silva?

Ms. Silva, formerly Mr. Campos’ running mate, assumed his position at the top of the Socialist ticket and pushed social democratic Aécio Neves into third place in polls.

Silva received huge support from the outset but has since suffered a decline in support. She controversially removed support for same-sex marriage from Campos’ program, as well as his support for laws to punish homophobia.

This predictably lost her the support of Brazil’s LGBT community, but gained her the growing and increasingly influential evangelical vote.

If that controversy left votes unchanged on balance, the same cannot be said for her economic policies, which have hurt her support. Controversial calls for a committee to search for the right people to run the country also led to attacks from the other candidates, and her support has since plunged.

Two other surveys have since confirmed the trends. The Ibope Institute and Datafolha have both predicted that Rousseff will win on Sunday with around 40% of the vote.

Ibope reports that Silva will receive 24% and Neves will come third with 19%. Similarly, Datafolha stated that Silva would receive 24% and Neves 21%.