Ms Rousseff said she wanted to be "a much better president" and promised political reform
The 66-year-old Rousseff, who was a Marxist guerrilla in her youth, overcame growing dissatisfaction with the economy, poor public services and corruption to narrowly clinch a second term for herself and the fourth in a row for her Workers' Party.
After a bitter, unpredictable campaign that pitted poorer Brazilians grateful for government anti-poverty programs against those exasperated with a stalled economy, Rousseff must now seek to continue flagship social services even as she tweaks economic policies to restore growth. Speaking to a relieved crowd of supporters on Sunday night in Brasilia, the capital, Rousseff acknowledged the close race and the call for change expressed by many voters.
"I know that I am being sent back to the presidency to make the big changes that Brazilian society demands," she said after winning the runoff election with 51.6 percent support. Her slim, three-point margin over centrist candidate Aecio Neves came largely thanks to gains against inequality and poverty since the Workers' Party first came to power in 2003. Rousseff's victory came just a year after massive street protests swept Brazil because many advances of the past decade had stalled.