Melgar moved top of the Peruvian Primera Division table as the chasing pack stumbled midweek.
Argentine striker Bernardo Cuesta's brace lifted Melgar to a 2-1 win over Cesar Vallejo at the Estadio de la Universidad Nacional San Agustin on Wednesday.
Cuesta got the ball rolling in the 25th minute with his sixth goal of the season, before Colombian defender Luis Cardoza levelled proceedings on the stroke of half-time.
But Melgar were not to be denied maximum points as Cuesta struck again 17 minutes from time.
With Juan Aurich and Inti Gas dropping points, Melgar (23 points) took a two-point lead atop the standings after 12 rounds.
Juan Aurich - second in the table - overturned a two-goal deficit to salvage a 2-2 draw at Real Garcilaso.
Free-falling Inti Gas suffered back-to-back defeats, this time losing 4-2 at home to Universidad San Martin, who were led by hat-trick hero Santiago Silva in a match marred by four red cards.
Inti Gas striker Fernando Oliveira and Universidad San Martin midfielder Benjamin Ubierna were both sent off nine minutes before half-time.
Raul Penalillo of Inti Gas and opposing substitute Carlos Ancues also saw red in the second half.
Universitario are also two points adrift of Melgar after they edged San Simon 1-0.
Los Caimanes and Alianza Lima played out a scoreless draw in the only other matches on Wednesday.
Meanwhile on Thursday, Victor Rossel scored in the 90th minute as Sport Huancayo downed Sporting Cristal 2-1.
The result helped Sport Huancayo off the foot of the table at Los Caimanes' expense.
Union Comercio accounted for Leon de Huanuco 1-0, while UTC Cajamarca were 2-1 winners against Cienciano.