Andres Manuel Lopez Obrador was sworn in as Mexico's next president Saturday, after the anti-establishment leftist won a landslide election victory promising to "transform" a country fed up with crime, poverty and corruption.
The leader, widely known by his initials as "AMLO," begins his six-year term with strong majorities in both houses of Congress -- but has caused market jitters in Latin America's second-largest economy with a style that some see as authoritarian and radical.
"I swear to defend the constitution of the United Mexican States and its laws, and faithfully and patriotically carry out the post of president of the republic that the people have entrusted to me," Lopez Obrador said with his right hand raised before the Congress.
Lopez Obrador is vowing to lead a sweeping "transformation" after 89 years of government by the same two parties.
Not everyone is persuaded by the brand of change he is promising: critics accuse the sharp-tongued, silver-haired leader of being an authoritarian radical, and Mexican stocks and the peso have plunged in recent weeks.
But Lopez Obrador, 65, has an undeniably strong mandate: he won a landslide victory in the July 1 elections, together with large majorities in both houses of Congress for his coalition -- led by the party he founded just four years ago, Morena.
It was the biggest win for any president, and the first for a leftist, since Mexico transitioned to multi-party democracy in 2000.
Lopez Obrador traveled to his swearing-in ceremony in his small white Volkswagen Jetta, making his way through a sea of supporters.
Jose Angel Mejia, 38, was in the crowd outside the lower house to fete the new president.
"It's a historic day, I still can't believe it," he said, raising his eight-year-old son's arm in the air in celebration.
"We're going to have a change at last."
After the ceremony, Lopez Obrador planned to go to Mexico City's central square, the Zocalo, for a second ceremony unlike any presidential inauguration in Mexican history: he will receive an indigenous chieftain's staff as shamans perform a purification ritual with incense and flowers.
The new president inherits a sticky set of problems from his unpopular predecessor, Enrique Pena Nieto.
They include endemic corruption, gruesome violence fueled by the war on drug cartels, and the caravan of 6,000 Central American migrants camped at the US-Mexican border -- not to mention the minefield that diplomacy with Mexico's giant northern neighbor has become under President Donald Trump.
Lopez Obrador, a former protest leader and Mexico City mayor, has been short on specifics regarding his plans for all of the above.
What he is promising, first and foremost, is a presidency like no other.
Vowing to lead his anti-corruption, pro-austerity drive by example, he has turned the presidential residence into a cultural center, plans to sell the presidential jet and fly commercial instead, wants to cut his own salary by 60 percent and has eliminated the presidential security detail.
A massive crowd of supporters is expected at the chieftain's staff ceremony, where, in between a series of concerts by famous musicians, Lopez Obrador will give a second speech from the National Palace.
That long-disused seat of power is where the new president plans to install his offices -- sending a message on the kind of change he represents.
The palace, with a history that dates to Aztec times and walls covered in murals by iconic painter and communist Diego Rivera, is a far cry from the current presidential headquarters, Los Pinos -- a sprawling complex that sits in a leafy park, isolated from the bustle of the capital.
The guest list includes a host of regional presidents, King Felipe VI of Spain, and US Vice President Mike Pence, accompanied by his boss's daughter and adviser, Ivanka Trump.
President Trump, who is at the G20 summit in Argentina, has struck up a surprisingly warm relationship with Lopez Obrador -- though the migrant caravan threatens to interrupt that honeymoon.
The American president is pressuring Lopez Obrador to accept a deal to keep asylum-seeking migrants in Mexico while their claims are processed in the United States.
Lopez Obrador's foreign minister, Marcelo Ebrard, is due in Washington on Sunday for talks on the issue with US Secretary of State Mike Pompeo.