Mexicans face a choice between three groupings. Morena is allied with the Labour Party and the Ecologist Green Party of Mexico. The main opposition is the Strength and Heart coalition, which combines the traditional parties, including rivals with differing ideas and agendas: the Institutional Revolutionary Party (PRI) that ruled Mexico for seven decades, the National Action Party and the Party of the Democratic Revolution. Citizens’ Movement is fielding candidates alone.

Morena’s coalition is unlikely to win the congressional supermajority which would allow it to alter the constitution. (It won one in 2018 but lost it again in 2021.) President Andrés Manuel López Obrador introduced a package of changes in February to do just that. It includes electing judges by popular vote, closing independent regulatory agencies and increasing government control of the electoral oversight authority. This package looks unlikely to pass.

Seven of Mexico’s 32 states are disproportionately important, accounting for close to 50% of all votes. They include Mexico City and Nuevo León, a northern state that is home to Monterrey, the business capital. Although Ms Sheinbaum is set to carry most of these key states in the presidential vote, the opposition could win in many of the other races.

Morena controls rural areas and poorer barrios of towns and cities. But places with richer, more educated populations tend to see more strategic voting patterns, says Daniel Linsker of Control Risks, a consultancy. Voters in Nuevo León and Jalisco, another important state for business, are expected to vote for Ms Sheinbaum, but for opposition parties in local elections.

Citizens’ Movement is betting on such split voting. While its presidential candidate is polling in low double digits, the governors of both states were elected from the party. “In these elections, cross-voting is urgently necessary to balance powers,” says Luis Donaldo Colosio, the Citizens’ Movement mayor of Monterrey.

Holding all the elections on one day will probably boost participation. But it is also likely to enforce a winner-takes-all dynamic that could favour the incumbent. According to Mr Linsker, this dynamic may be particularly strong in elections for Congress, since most Mexicans do not know their candidates. “So they simply end up voting for the same party as for the presidency,” he explains.

Morena, more of a López-Obrador fan club than a party, may lose steam once he leaves the presidency. A third of its governors elected since 2018 used to be members of PRI. They made Machiavellian jumps into Morena to stay in power. The elections are likely to leave Mexican politics in flux once again.

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