Leaders Palmeiras lose again in Brazil
The league leaders, who are four points ahead of second-placed Atletico Mineiro, have lost their last three matches without scoring and gone four games without a victory.
They have only managed to retain their lead thanks to poor results by their challengers.
Mineiro, who are at home to Vitoria on Saturday, have lost two of their last three matches and third-placed Internacional, who face Gremio on Sunday, have drawn their last two.
Striker Nunes scored both goals for Santo Andre, who pulled clear of the relegation zone on goal difference, while Palmeiras forward Obina twice hit the woodwork.
Nunes opened the scoring in the 20th minute when he tapped in left back Camilo's low cross after a poor clearance by the Palmeiras defence.
With 13 minutes left, the same combination of Camilo passing and Nunes finding the net gave Santo Andre their second goal.
Palmeiras goalkeeper Marcos said: "When the team are winning, you have an excess of confidence and that can mislead you... That excess turned into a lack of confidence with the setbacks."