Goalkeeper Marcos was sent off in the 35th minute for a penalty on Jorge Henrique from which Ronaldo put Corinthians ahead but they snatched a point six minutes from time.
With five matches to go, Palmeiras are equal on 58 points with title holders Sao Paulo, who beat Barueri 1-0 on Saturday, and ahead on goal difference.
Atletico Mineiro are third, two points behind after a 3-2 away win over Goias, while Flamengo, 1-0 winners against Santos on Saturday, are two points further back in fourth, the last of the Libertadores Cup qualifying berths.
Internacional slipped out of the top four with a second successive 1-0 defeat, this time at home to Botafogo whose victory kept them clear of the relegation zone.
Defender Danilo equalised for Palmeiras six minutes after halftime but former FIFA World Player of the Year Ronaldo scored again in the 65th from Argentine Matias Defederico's pass.
Central defender Mauricio squared the ledger, however, heading in a cross from Chilean full back Luis Figueroa.
TASTE OF VICTORY
"It was a draw that tastes like a victory because of everything that happened," said Brazil midfielder Diego Souza of Palmeiras.
"We lost a leader like Marcos, were left a man short ... but Muricy (Ramalho) got the tactics right, we equalised, we conceded the second and we went up and levelled again," he added, referring to Palmeiras' coach.
Ronaldo, who lost almost a year following a third knee operation, took his tally this season to 21 goals in 34 matches since returning to Brazil from Europe, where he shone with Inter Milan, Barcelona, Real Madrid and AC Milan.
At the wrong end of the standings, Fluminense maintained their hopes of avoiding relegation with a 3-2 upset win away against sixth-placed Cruzeiro, their third victory in five matches and sixth in a row undefeated.
Defender Jonathan and striker Wellington Paulista put Cruzeiro two goals up early, but Fluminense hit back through defender Gum and former Olympique Lyon striker Fred, who scored twice against his former club, to lift Fluminense off the bottom.
