BRASILIA, Oct. 31 (Xinhua) -- Dilma Rousseff, presidential candidate for Brazil's ruling Workers Party (PT), was officially declared president-elect Sunday by the Superior Electoral Tribunal (SET).

With 93.25 percent of votes already counted, Rousseff won 55.43 percent of valid votes and has 51.59 million votes. Her opponent, Jose Serra, got 41.48 million votes, or 44.57 percent, according to the SET.

Rousseff, 62, is considered the main manager of President Luiz Inacio Lula da Silva's government.

She was born in Minas Gerais state and had a strong trajectory against the military dictatorship of 1964-1985 and at the public service in order to make it democratic at the end of the dictatorship.

She joined the PT in 2001 and was Energy Minister during the first term of Lula since 2003. Later in June 2005 she was appointed chief of staff of Cabinet.

The president-elect will be inaugurated in on January 1, 2011.