Last season's runners-up Benfica beat 10-man Rio Ave 3-1 away while Lisbon rivals Sporting eased past 10-man Pacos de Ferreira 4-0, moving to the top of the table, both on 26 points from 11 matches. Sporting have the better goal difference.
They dislodged Porto, who were stunned by a 1-0 defeat at Academica de Coimbra on Saturday, missing a penalty and a pair of great chances in the process.
The 'Dragons' are now two points behind.
Benfica's Brazilian striker Lima unlocked a thorny match for 'the Eagles' with a second-half brace against well-drilled Rio Ave.
Sporting in turn, relied on the services of Colombian sharpshooter Fredy Montero, who also bagged a brace in their comfortable home win over Pacos de Ferreira.
"We are extremely pleased, this is the fruit of a lot of hard work this season. We know where we are heading," Sporting coach Leonardo Jardim told Portuguese television Sport TV.
His mood contrasts with their northern rivals.
Porto coach Paulo Fonseca is under pressure after an under-par run that included their first league defeat in 53 matches and a disappointing Champions League home draw with Austria Vienna in midweek.
The team bus was met by angry fans upon arrival in Porto late last night. TV footage showed about 100 fans chanting "please play some football", kicking the bus and throwing firecrackers against it.
"Of course there is pressure, Porto is a club used to winning. We don't like this and cannot be happy. Our performance was far from what we can do," Fonseca said.
- Sports & Recreation