Leftist economist Luis Arce assumed the Bolivian presidency on Sunday in a ceremony attended by foreign leaders, facing the challenge of uniting a deeply polarised society and reviving a virus-wracked economy.
Arce, who won election easily last month, was sworn in by newly invested Vice-President David Choquehuanca in the presence of parliamentarians, ordinary Bolivians and guests including King Felipe VI of Spain, President Alberto Fernández and the leaders from Colombia and Paraguay.
His right hand raised, he pronounced the words "I swear," beginning his term as president.
"We are beginning a new stage in our history," he said later in a speech, "and we want to do so with a government that is for everyone, without discrimination of any kind. Our government will seek to rebuild our homeland in unity."
Colombian President Iván Duque later met with Arce and said Bogota hoped to "continue strengthening trade, security and diplomatic relations" with La Paz within the framework of the Andean Community of nations, of which Colombia holds the rotating presidency.
The political rise of Arce, who served as economy minister to President Evo Morales, marks the return to power of the Movement for Socialism (MAS) after Morales renounced his office and fled the country in June 2019 amid widespread social protests.
As Morales's heir apparent, Arce scored a resounding first-round victory in the October 18 elections, outpolling his chief challenger, centrist Carlos Mesa, by 26 points.
Morales returned Monday from the border with Argentina, the country where he had sought refuge after first fleeing to Mexico.
He then headed to the central coca-growing region of El Chapare, where he has strong support among the rural population.
Analysts say Arce's biggest challenge may be to convincingly demonstrate that he really is in charge, and not simply being manipulated by the long dominant Morales.
He will have to do so while juggling numerous other difficulties.
Bolivia's politics are hugely polarised between east and west, cities and the countryside.
And there are accusations of resurgent racism and courts that serve the government rather than justice.
Morales drew praise for presiding over Bolivia's "economic miracle" – with Arce as his finance and economy minister – but he was often lambasted for his authoritarian style.