Left-wing candidate Andrés Manuel López Obrador has claimed victory in Mexico’s presidential election, saying “profound change” is coming.
The ex-Mexico City mayor, known by his initials Amlo, is projected to win about 53 percent. His rivals have conceded in a crushing defeat for the main parties.
Mr López Obrador’s key pledge has been to tackle corruption.
He has also been highly critical of President Donald Trump and ties with the US will now be closely watched.
Relations with Washington have been hugely strained, with Mr Trump strongly criticising Mexico over trade and migration.
Mr Trump has sent a tweet of congratulations.
Late on Sunday, the 64-year-old promised to respect civil liberties and said he was “not looking to construct a dictatorship, either open or hidden”.
Some opponents have expressed fears that his leftist and populist policies could damage the already sluggish economy and turn Mexico into “another Venezuela”, which is suffering a deep economic crisis and rampant inflation.
Hailing a “historic night”, Mr López Obrador called on all Mexicans to reconcile and repeated his campaign pledge to review energy contracts for signs of corruption.
“Corruption is…the result of a decadent political regime. We are absolutely convinced that this evil is the main cause of social and economic inequality, and also that corruption is to blame for the violence in our country,” he said.
He has insisted that no-one involved in corruption will be spared, not even those he calls “brothers-in-arms”.