Rousseff, a pragmatic leftist expected to seek a second term next October, won 47 percent support in the most widely expected matchup – up from 42 percent in last month's poll.
Senator Aecio Neves of the traditional opposition party PSDB took 19 percent and Pernambuco Governor Eduardo Campos, whose center-left PSB party recently broke with the governing coalition, polled at 11 percent.
Neves and Campos, who are still introducing themselves to a national audience, took 21 percent and 15 percent respectively in the October Datafolha poll.
Rousseff's popularity is recovering from widespread demonstrations in June against shoddy public services. Popular social programs and nearly record-low unemployment have bolstered her support despite sluggish economic growth.