Bolivian President Evo Morales' leftist party appears to have won a narrow majority in a new assembly picked to rewrite the constitution.
The president has promised to give the people their say
Early unofficial results suggested he won 133 out of 255 seats - short of the two-thirds majority needed for full control - but Mr Morales was upbeat.
"This support ... gives us the strength to go on changing," he said.
Meanwhile four of the country's nine regions seem to have voted strongly in favour of greater autonomy.
The president is opposed to the moves to give regions more powers.
Santa Cruz, Tarija, Pando and Beni states are all rich in the country's natural resources.
Some of the other regions, such as the Quechua and Aymara states, were expected to reject the proposal.
The country has already seen radical change since President Morales took office in January. "We want to be an exemplary country in Latin America with the participation of the people. That is what is historical about today," President Morales told reporters.
More than 100 observers from the Organization of American States (OAS) and European Union had been sent to the country and were analysing results from some of the 23,000 voting stations.
"We are continually receiving reports from the entire country and so far they are favourable," said Horacio Serpa, an observer from the OAS.
President Morales has nationalised the oil and gas industries, begun redistributing land, cut public sector salaries and hopes to promote some legal uses of coca leaves.
Many in provinces such as gas-rich Santa Cruz want autonomy
Coca is the raw material used in producing cocaine, but the leaf also has widespread ceremonial and medical uses in Bolivia.
Some have called the changes in Bolivia a democratic revolution.
But whatever it is, Evo Morales appears determined to continue with the radical reforms he has been implementing in what is the poorest country in South America, said the BBC's South America correspondent Daniel Schweimler.
The assembly will meet in August and spend between six months and one year drawing up a new draft constitution that will then be voted on by the people.
If President Morales' party wins a majority, he will continue with the reforms he has been implementing since he took office.
They include plans to give a greater voice to the majority indigenous population, tighter state control of the economy and more transparency in what has traditionally been a corrupt political system.
Mr Morales came to power after years of turmoil which saw two recent governments toppled by violent street protests.
Himself an Aymara Indian, he promised Bolivia's majority indigenous population a greater share of the country's wealth and an end to years of corrupt government by a wealthy elite. But his close ties to radical governments in Venezuela and Cuba and the fast pace of change have worried some, both inside and outside Bolivia.
This vote is a move, as promised, to let the people have their say and a poll on how President Morales has done so far.