MEXICO CITY (AP) — Mexicans in two states, including the country’s most populous, will elect new governors Sunday, having only known single-party rule for nearly a century.

The State of Mexico hugs Mexico City on three sides, encompassing urban sprawl and rural ranches, as well as stunning inequality, violence and corruption. For decades it has been the heart of the Institutional Revolutionary Party.

But its voters could be ready to finally oust the PRI in favor of President Andrés Manuel López Obrador’s Morena party, in a race closely watched as a preview of the 2024 presidential election.

Morena candidate Delfina Gómez, a schoolteacher making her second bid for the post, has held a healthy lead in recent polling over Alejandra del Moral. The former mayor representing the PRI has struggled to attract a fed-up electorate bent on change.

Del Moral is not only the PRI’s hope. She leads a bizarre coalition including the conservative National Action Party and leftist Party of the Democratic Revolution that have only in common the desire to deny López Obrador’s party control of Mexico’s largest state electoral prize.

Gómez has campaigned largely on the far-reaching support for López Obrador’s popular social programs.

On Friday, the president said he hoped for a calm vote and was “very, very optimistic.” His party is also viewed as the favorite in next year’s presidential election. Even though it has not yet selected its candidate, it has a couple of strong possibilities and the opposition is generally considered to be in disarray.

Voters in the sparsely populated northern border state of Coahuila, where the PRI remains competitive, will also select a new governor Sunday. But even if the PRI holds on there, the loss of the State of Mexico could spell the end of its political relevance on a national stage, a stunning reversal for a party that ruled Mexico uninterrupted for seven decades.