SAO PAULO - Ruling party candidate Dilma Rousseff is pulling ahead in Brazil's presidential race, gaining momentum as the focus of the campaign shifts away from social issues and back to the economic gains of recent years.

Rousseff extended her lead over opposition challenger Jose Serra to 10 percentage points in a new opinion poll released on Friday. It was the third poll this week to show her gaining ground after a rough few weeks in which a re-energized Serra narrowed the gap.

The survey by polling firm Datafolha showed Rousseff with 50 percent of voter support versus 40 percent for Serra, according to the online edition of Folha de S. Paulo newspaper, which commissioned the poll.