The PRI and its ally UDC gained control of the Coahuila state Congress after winning all 16 majority districts and likely two more through proportional representation.
Computations for the Coahuila Congress elections, which renewed all 25 seats, took place last week. The PRI in alliance with the Unidad Democrática de Coahuila secured its hold on the state.
The vote unfolded amid the World Cup and public protests. Morena refused to accept the outcome and alleged irregularities including vote buying through QR codes.
Morena figures such as Ariadna Montiel and Ricardo Monreal pointed to possible fraud. The ruling party faced criticism over its campaign performance.