Two Mexican opposition candidates on Sunday vowed to take a tougher line against U.S. President Donald Trump’s border wall, at events where they were selected by their parties to seek the presidency in a July 1 election.

Andres Manuel Lopez Obrador, 64, of the leftist Morena party holds a double-digit lead in recent polls although right-left coalition leader Ricardo Anaya has recently gained traction.

Former finance minister Jose Antonio Meade, 48, nominated on Sunday by the ruling Institutional Revolutionary Party (PRI), trails behind Lopez Obrador by as much as 20 points.

Lopez Obrador told several hundred Morena supporters gathered at a Mexico City hotel that Trump’s plan for a U.S.-Mexico border wall is unnecessary and bound to leave problems unresolved.

“If he insists on building the wall, we’re going to turn to the United Nations to defend the rights of Mexicans,” he said. “I‘m conscious of my historic responsibility.”

The former Mexico City mayor who has run twice for the presidency also promised to combat inequality, crime and corruption, key election issues for all of Mexico’s main political parties.

Anaya echoed Lopez Obrador’s opposition to a U.S.-Mexico border wall, refusing to pay for its construction and saying he would be tougher than the PRI to defend Mexico’s independence.

“Mexico will never again be treated like a doormat for the United States, as it’s been in this government,” said Anaya, who is backed by the center-right National Action Party (PAN) and the center-left Party of the Democratic Revolution (PRD).

The youngest of the three candidates, Anaya, 38, said in a CEO-style presentation at an auditorium in the capital that he would fight public corruption, raise the minimum wage and improve education to support an economy based on “knowledge” rather than “manufacturing.”

Meade pledged in his nomination acceptance speech at a Mexico City stadium to crack down on crime and impunity, issues that have dogged the current administration and hurt the PRI’s credibility.

With six weeks to go before campaigning begins for the July 1 vote, Meade’s campaign says early polls have traditionally been unreliable indicators of final results in Mexico.

“If this trend continues, the race will become more competitive between the two front runners,” political risk analysts at Eurasia Group said in a note on Friday. “But voter intentions have historically shifted throughout the campaign season, so much could change.”

Analysts have said Lopez Obrador could slow the pace of President Enrique Pena Nieto’s opening of the state-run energy sector to private investment, but they expect he would face a divided Congress that would make any rapid shifts in policy unlikely.

Still, some international investors are concerned he could undermine decades of free-market reforms in Mexico.

The election will mark the first time independent candidates can run for the presidency. Margarita Zavala, wife of former President Felipe Calderon from the PAN, and Jaime Rodriguez Calderon, who became Mexico’s first independent governor in 2015, are expected to get enough signatures to run.

Analysts doubt any of the potential independent candidates have a chance, but their supporters could be a factor in the outcome in a close race.