Sunday's referendum has featured seven questions including reintroducing term limits to prevent presidents from running indefinitely.
Ecuadorans went to the polls on Sunday to decide the political fate of former president Rafael Correa in a referendum called by his successor turned staunch opponent that is expected to prevent the ex-leader's return to power.
Correa is locked in a battle with President Lenin Moreno for control of their deeply divided leftist ruling Country Alliance party.
Sunday's referendum, in which Moreno backs the "yes" vote, featured seven questions including reintroducing term limits to prevent presidents from running indefinitely.
If the current head of state gets his way, Correa will not be able to join the 2021 election race.
Voting ended late on Sunday. The National Electoral Council said the ballot "took place normally" with no significant incidents to report. It was expected to give preliminary results around 8:00 pm (0100 GMT).
According to surveys, the "yes" camp -- supported by traditional opposition parties -- was predicted to win a comfortable majority with between 72 and 84 percent of the vote.
Moreno, as he voted in the north of the capital Quito, said the result would be "transcendental for the future of the country, so that our children are protected, so that corrupt people do not return to mock us... for the care of the environment, for economic reactivation."
Margin of result is key
Upon entering office last May, Moreno -- Correa's deputy between 2007 and 2013 -- transformed into a steadfast critic of his predecessor, whom he has called a proponent of "21st century socialism" and accused of leading a corrupt government.
Far from keeping Correa's presidential seat warm as expected, Moreno's calling of the referendum instead spells a clear invitation to enter a post-Correa era.
On top of the question regarding indefinite re-election -- a law approved by Correa in 2015 -- Moreno proposes restructuring the body created by his former ally to select senior authority figures such as judges.
In practical terms, removing its current members would represent a total "de-Correazation" of the state.
"The margin (of victory) is what has to be looked at. If Lenin Moreno wins by a big margin, he will achieve the fundamental objective of the vote: legitimacy," political expert Simon Pachano said.
Moreno, 64, only narrowly defeated conservative banker Guillermo Lasso in last April's election.
"All the 'no' votes will be Rafael Correa's. Suppose you have 40 percent, he can claim that and say we are the first political force in the country," Pachano added.
Correa, who ruled for a decade from 2007, has branded Moreno a "traitor" and the vote "unconstitutional," denouncing the president for wanting to achieve "absolute rule."
Focus on corruption
He also maintains that with a question over whether those convicted of corruption should be barred from politics, Moreno is trying to erect legal pretexts to prevent Correa re-entering office.
"They will invent a crime against me to disable me. It is the right's new strategy to destroy progressive leaders," Correa, 54, said.
But he asserted his political stance against big odds has borne fruit by swaying a substantial proportion of voters.
"Independently of today's results, we have already won," Correa said on Twitter on Sunday. "The treason and the most unfair campaign in contemporary history has brought out the best in us!"
Correa -- who returned to Ecuador from Belgium in January to embark on a solo "no" campaign -- is expected to testify in court on Monday over alleged irregularities in million-dollar oil sales to China and Thailand made during his tenure.
His former vice president, Jorge Glas, was sacked by Moreno following his re-election and sentenced to six years in jail for corruption.