UPDATE 4-Exit polls show Mexicans overwhelmingly voted for leftist Lopez Obrador

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* Lopez Obrador would be first leftist president in decades

* Exit polls show him far ahead of two main rivals (Recasts with exit polls)

MEXICO CITY, July 1 (Reuters) - Mexicans voted overwhelmingly for anti-establishment outsider Andres Manuel Lopez Obrador in Sunday's presidential election, exit polls showed, betting a leftward turn in government could end the corruption and violence that has blighted the country.

One exit poll by polling firm Parametria showed Lopez Obrador, a former Mexico City mayor, winning between 53 percent and 59 percent of the vote, far ahead of his two main rivals from Mexico's traditional ruling parties.

Consulta Mitofsky for broadcaster Televisa showed the leftist, who had maintained a healthy lead in polls ahead of the vote, winning between 43 percent and 49 percent of the vote. Parametria, Mitofsky and others showed him winning by at least 20 percentage points.

An official "quick count" of results is expected at midnight EDT (0400 GMT), with a margin of error of 0.5 percent.

Lopez Obrador, 64, is expected to move Mexico in a more nationalist direction if he wins and could exacerbate simmering tensions with U.S. President Donald Trump and unsettle some investors.

He would be the first leftist president in decades in Mexico, and has pledged to reduce the country's economic dependence on the United States. The current government has sparred with Trump over trade and migration for months.

If confirmed, the results would represent a resounding defeat for outgoing President Enrique Pena Nieto's ruling centrist Institutional Revolutionary Party (PRI). The PRI has ruled Mexico for all but 12 of the last 89 years.

The runner-up in the 2006 and 2012 presidential elections, Lopez Obrador pitched himself as the only one capable of cleaning up the government after years of poor economic growth and rampant gang violence eroded faith in the political class.

Seeking support from economic nationalists, leftist liberals and social conservatives, Lopez Obrador has been vague on policy details. But he vows to reduce inequality, improve pay and welfare spending and run a tight budget.

(Reporting by Christine Murray and Diego Oré Additional reporting by Dave Graham, Noe Torres, Daina Beth Solomon Editing by Frank Jack Daniel, Jeffrey Benkoe and Paul Simao)