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MEXICO CITY (Reuters) - Mexican leftist candidate Andres Manuel Lopez Obrador’s commanding lead over his closest rival narrowed slightly to 12 percentage points ahead of Sunday’s presidential vote, according to a GEA/ISA poll published on Monday.

The survey showed Lopez Obrador, a former mayor of Mexico City, with 35 percent of the preferences in a poll conducted between June 15 and 17, compared to 37 percent of a survey in late May.

The 64-year-old Lopez Obrador, who is on his third bid for the presidency, has capitalized on growing frustration with the ruling party over record levels of violence, a series of political corruption scandals and sluggish economic growth.

Support for his closest rival, Ricardo Anaya, who leads a right-left coalition, held steady at 23 percent according to the nationwide survey of 1,070 people in their homes. The poll had a margin of error of +/- 3 percentage points

Backing for Jose Antonio Meade, candidate of the ruling centrist Institutional Revolutionary Party (PRI), rose to 21 percent from 17 percent in the previous survey.