Brazil's 143 million voters Sunday are deciding who will lead the world's seventh largest economy as polls opened across the South American country in the tense presidential runoff race, dpa reported. President Dilma Rousseff, 66, of the centre-left Workers' Party (PT), is defending her office for another four years. Her challenger is Aecio Neves, 54, a senator from the centre-right Party of Brazilian Social Democracy (PSDB). Polls are to close at 1800 GMT, with results expected early Monday morning. The victor will be sworn into office on January 1, 2015, for a four-year term. Voters will also choose senators and governors.