NAUCALPAN, MEXICO -- Mexicans in two states, including the country's most populous, were voting to 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 Andres Manuel Lopez Obrador's Morena party, in a race closely watched as a preview of the 2024 presidential election.

Morena candidate Delfina Gomez, 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 Lopez Obrador's party control of Mexico's largest state electoral prize. She voted Sunday in Cuautitlan Izcalli, a suburb northwest of Mexico City.

Gomez has campaigned largely on the far-reaching support for Lopez Obrador's popular social programs. She voted early on a warm and sunny Sunday in a school in Texcoco, east of Mexico City.

"We want change, for them to pay attention to us," said Rufina Perez, a retiree living in Naucalpan, a suburb west of the capital. "They all made us promises, PRI, PAN already passed and we know how it was," she said, expressing confidence that it would be different with Morena in charge.

There were also those who demanded change, but cast their votes for del Moral.

"In the State of Mexico security worries us the most," said Victor Manuel Olmos, who identified himself as a PAN voter also from Naucalpan.

Socorro Hernandez was more focused on problems she saw at the federal level. She said it was "very important" that she voted Sunday to show disagreement with Lopez Obrador's party.

In Huehuetoca, north of Mexico City, Alejandra Santillan Torres, a 29-year-old homemaker, said "the elections are important so that they take into account the workers."

She said she voted for the governing PRI, as she has in the past, because she felt they were doing well.

On Friday, the president said he hoped for a calm vote and was "very, very optimistic." His party is also viewed as the favourite 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.

Morena's national president Mario Delgado complained early Sunday that there was an operation of "persecution, harassment and intimidation" against the party's supporters in Coahuila. The state government responded in a statement that it was only carrying out normal security operations.

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AP writer Emilio Lugo in Huehuetoca, Mexico contributed to this report.