Earlier strikes from Hernan Barcos and Ze Roberto appeared to have put the home side in control but struggling Portuguesa hit back thanks to an own goal from Rhodolfo and a Luis Ricardo equaliser.
But having been reduced to nine men following the dismissals of Bruninho and Valdomiro, the visitors could not hold out and Kleber settled it.
Internacional moved up to fifth after winning 3-1 at Ponte Preta.
A William penalty after 26 minutes gave the second-from-bottom hosts a shock lead but goals from Juan, Andres D'Alessandro, also from the spot, and Ignacio Scocco turned it around.
Substitute Diego Biro-Biro scored the winner as defending champions Fluminense beat Bahia 1-0 while Thiago Cardoso was on target in Santos' 1-0 defeat of Goias.
Neto Berola scored an 86th-minute equaliser as Atletico Mineiro salvaged a 1-1 draw from their trip to Vitoria, for whom Marquinhos netted.