The visit comes as the new U.S. administration ramped up an immigration crackdown and launched deportation raids of undocumented immigrants in several U.S. cities over the past week. Mr. Trump also has shocked Mexicans with his insistence that Mexico will pay for a new border wall, and his attacks on U.S. companies that open factories in Mexico.
“We must confront this campaign of hate and human-rights violations,” Mr. López Obrador said, adding that the crackdown on migration is the result of unrest, unemployment and low income that fueled a nationalist backlash in the U.S. “Low income and unemployment isn’t the result of hiring Mexican workers, but of flawed government policies.”
Mr. Trump’s complaints about the U.S. trade deficit with Mexico are misleading, he said, since most Mexican exports to the U.S. have significant U.S. components. “If Mexico was unfairly benefitting from [the North American Free Trade Agreement], then Mexico wouldn’t suffer economic stagnation and emigration, as it is right now.”
In Mexico City earlier Sunday, thousands took to the capital’s central thoroughfare to protest the border-wall plan, while criticizing Mexican President Enrique Peña Nieto and the ruling PRI party.
Mr. Peña Nieto faces rising political pressure to defend Mexico’s national pride, even as both countries get ready to renegotiate Nafta.
Mr. López Obrador’s visit to the U.S. appears to be designed to send a clear message: He will stand up to Mr. Trump, who he has called arrogant and autocratic, and branded his plans as foreign aggression.
“No one believed Mr. Trump’s campaign promises at first, but you can now feel the tension,” said Israel Robles, a truck driver from Puebla state who migrated to Los Angeles 25 years ago. “The Mexican community in the U.S. is now waking up and beginning to organize as his administration steps up deportations.”
Like Mr. Trump, the Mexican politician has cast himself as a political outsider challenging a corrupt and incompetent political “mafia.” Both men also share a mistrust of globalization, with Mr. López Obrador calling on Mexico to focus on its domestic economy rather than exports.
AMLO, as he is widely known, “speaks truth to the power and is close to the people,” said Salvador Irigoyen, a 21-year-old university student.
The visceral personality of Mr. López Obrador has often been compared with that of Mr. Trump. “His weakest point is his intolerance and arrogance. Whoever doesn’t agree with him is his enemy. He is in the tradition of the Latin American strongman,” said Fernando Belaunzarán, a lawmaker with the leftist Democratic Revolution Party, which Mr. Lopez Obrador abandoned in 2012 to create his own party.
Yet this time around, he is also adopting a more moderate tone in the hopes of broadening the appeal of his nationalist movement. He recently appointed Mexican businessman Alfonso Romo to prepare his campaign platform and economic-policy proposals.
“The goal is to generate trust, we don’t want to trigger instability nor harm rule of law,” said Mr. Romo, the owner of local Vector brokerage firm.
The author of more than a dozen books on Mexican politics and history, Mr. López Obrador has promised to triple growth rates to an annual 6% and broaden welfare plans. He also wants to lower Mexico’s high dependency on U.S. corn and gasoline imports, goals that have been criticized as unrealistic and protectionist.
Mr. Romo said Mr. López Obrador won’t upend economic stability nor interfere with markets should he become a candidate and win the presidency. That includes preserving central bank independence and open capital markets.
One of Mr. López Obrador´s policy proposals is a referendum to overturn Mexico’s historic 2013 opening of the oil industry to private investment. Mr. Romo said existing contracts wouldn’t be canceled, but said they would be renegotiated.
“We can’t breach contracts. I don’t see a new government imposing itself unilaterally,” Mr. Romo added.
Mr. López Obrador has been on a long campaign since 2005, ahead of his first bid for the presidency, which he narrowly lost the following year. He refused to concede defeat and declared himself Mexico’s legitimate president, blocking the capital’s Paseo de La Reforma boulevard for weeks with his supporters. In 2012, he lost to Mr. Peña Nieto by 7 percentage points.
Not everyone is convinced the third time will be a charm for the leftist politician.
“What surveys show at this stage is how well-known a politician is, because there are no formal presidential candidates yet,” said Ulises Beltrán, head of local polling firm BGC. “Mr. López Obrador always begins the race up high because of this factor, and also because of his populist rhetoric. But then his lead tends to narrow as the election nears.”
—Robbie Whelan contributed to this article.Write to Juan Montes at email@example.com