MEXICO CITY, Mexico (AFP)— Mexicans voted Sunday in a presidential election dominated by two women — a historic first in a country plagued by rampant criminal and gender-based violence.

Thousands of troops were deployed to protect voters, following a particularly bloody electoral process that has seen more than two dozen aspiring local politicians murdered.

Ruling party candidate Claudia Sheinbaum, a former Mexico City mayor and a scientist by training, had a 17 percentage point lead over her main opposition rival Xochitl Galvez in opinion polls on the eve of the vote.

“It’s a historic day. I feel very happy,” Sheinbaum, 61, told reporters before heading to a polling station in the capital, declaring “Long live democracy!” after casting her ballot.

The only man running, centrist Jorge Alvarez Maynez, was trailing far behind in polling.

It means that, barring a huge surprise, a woman is almost certain to break the highest political glass ceiling in Mexico, where around 10 women or girls are murdered every day.

“A female president will be a transformation for this country, and we hope that she does more for women,” said Clemencia Hernandez, a 55-year-old cleaner in Mexico City.

“Many women are subjugated by their partners. They’re not allowed to leave home to work,” she said.

Mariana Nieves, a 28-year-old designer, said a lot of younger Mexicans were fed up with politicians.

“I’m happy that a woman is going to win but I’m not very excited because I think neither of them has coherent proposals” on improving women’s rights, she said.

Nearly 100 million people were registered to vote in the world’s most populous Spanish-speaking country, home to 129 million people.

Sheinbaum owes much of her popularity to outgoing President Andres Manuel Lopez Obrador, a fellow leftist and mentor who has an approval rating of more than 60 per cent but is only allowed to serve one term.

In a nation where politics, crime and corruption are closely entangled, ultra-violent drug cartels have gone to extreme lengths to ensure that their preferred candidates win.

Hours before polls opened, a local candidate was murdered in a violent western state, authorities said, joining at least 25 other political hopefuls killed this election season, according to official figures.

The victims “are not here on this day and that’s very sad,” Galvez told reporters while going to vote.

In another sign of the difficulties of staging elections in cartel hotspots, voting was suspended in two southern municipalities because of violence, local authorities said Saturday.

Sheinbaum has pledged to continue the outgoing president’s controversial “hugs not bullets” strategy of tackling crime at its roots.

Galvez, 61, has vowed a tougher approach to cartel-related violence, declaring “hugs for criminals are over.”

More than 450,000 people have been murdered and tens of thousands have gone missing since the government deployed the army to fight drug trafficking in 2006.

The next president will also have to manage delicate relations with the neighboring United States, in particular the vexed issues of cross-border drug smuggling and migration.

Addressing a cheering crowd of thousands at her closing campaign rally, Sheinbaum said Mexico was going to “make history” by choosing its first woman president.

“I say to the young women, to all the women of Mexico — colleagues, friends, sisters, daughters, mothers and grandmothers — you are not alone,” she said.