A Georgian billionaire who is the main rival to President Mikheil Saakashvili in the country's parliamentary election has refused to vote.
Bidzina Ivanishvili said the authorities had "already resorted to very many violations", as Georgia's 3.6 million voters went to the polls.
It is seen as the biggest test of President Saakashvili's popularity since he came to power in 2003.
Mr Ivanishvili, Georgia's richest man, accused him of human rights abuses.
He described it as "something close to a democratic election" but accused Mr Saakashvili of "distorting" the constitution, and said that was why he would not vote. His wife, who was with him at the polling station, did cast her ballot.
Despite the flaws, Mr Ivanishvili said, "today for the first time in Georgian history the government will be changed through elections".
His Georgian Dream coalition urged supporters to rally in the centre of the capital Tbilisi on Monday evening "to celebrate victory together and defend our votes".
Analysts say the election is crucial because Georgia's political system is being altered to give more power to parliament.
The first exit polls are expected shortly after voting ends at 20:00 local time (16:00 GMT).
President Saakashvili's United National Movement has 119 of the 150 seats in the outgoing parliament.
Mr Ivanishvili, who made his fortune in Russia in the early 1990s, is now deemed legally entitled to vote, despite an earlier dispute about his citizenship.
He was stripped of his Georgian citizenship last year, but then a constitutional change was made which would allow him to vote as a French passport holder and EU citizen.
Mr Saakashvili says his opponent would allow Russia to dominate the former Soviet republic.
The president led the country in a short war with Russia in 2008.
He has sought to portray the election as a choice between his progressive Western-leaning government, and a future dominated by Russia.
"Tomorrow, our enemy has its last chance to turn us off our path of independence," Mr Saakashvili said in a recorded address carried on state TV on Sunday.
The human rights group Amnesty International says many of Mr Ivanishvili's supporters were "fined, fired, harassed or detained for expressing their political views" during the election campaign.
"In a highly charged political environment, public officials associated with the ruling party have on occasion abused public institutions and administrative resources to restrict the freedom of assembly, expression and association of opposition supporters," Amnesty's Georgia expert Natalia Nozadze said.
The government's reputation has taken a battering in recent weeks because of a prisoner-abuse scandal.
Videos broadcast on national television showed prison inmates being beaten and sexually abused by guards.
The scandal sparked street protests and has allowed Mr Ivanishvili to portray the government as high-handed and uncaring.
Mr Saakashvili's second term as president ends next year, and he is constitutionally barred from standing again.
A parliamentary majority for his United National Movement could see him continue his domination of Georgian politics after he steps down.
The BBC's Damien McGuinness in Tbilisi says fist-fights are already a common feature of campaign meetings, and there are fears a dispute over the results could lead to violence.