A banner of the Institutional Revolutionary Party (PRI) is pictured behind a statue of the General Lazaro Cardenas del Rio at PRI headquarters in Mexico City, Mexico, July 11, 2017. REUTERS/Edgard Garrido

MEXICO CITY (Reuters) - Mexico’s ruling Institutional Revolutionary Party (PRI) said on Thursday registration for PRI contenders in the July 2018 presidential election will begin on Dec. 3, and that a national convention would pick the candidate on Feb. 18.

In a statement, the PRI said the national convention would be made up of around 19,100 delegates to be chosen during the second week of December. President Enrique Pena Nieto is barred by law from seeking a second six-year term.

Ruling Mexico continuously from 1929, the PRI had become a byword for corruption by the time it was voted out in 2000.

Pena Nieto returned the party to power in 2012, but a slew of corruption scandals, ongoing gang violence and anemic growth have sapped the PRI’s credibility in the past five years.

The party faces an uphill struggle to hang on to power, and veteran leftist Andres Manuel Lopez Obrador, twice a runner-up for the presidency, has led most early polling for 2018.

The run-up to the election takes place in the midst of fraught discussions between Mexico, the United States and Canada over the future of the North American Free Trade Agreement (NAFTA), which underpins much of the region’s commerce.

U.S. President Donald Trump has threatened to walk away from the accord if he cannot rework it in favor of the United States. The three nations have pledged to keep talking through March.