Bulgarians are voting in a snap poll on Sunday after a previous election in April produced a fragmented parliament that failed to form a viable coalition government.
Latest opinion polls suggest that the rerun could produce similar results but also a further drop in support for former Prime Minister Boyko Borissov's GERB party, after the current caretaker government made public allegations of widespread corruption during his rule.
NATO and EU member Bulgaria has been repeatedly criticized for not tackling corruption and for deficiencies in the rule of law and media freedom.
The anti-corruption campaign of Borissov's opponents was additionally boosted by the sanctions the US Treasury imposed last month against several Bulgarian public officials and business leaders for corruption.
Polls suggest a tight race between Borissov's party, which came first in April with over 26 per cent of the vote, and its main rival, the anti-elite. There is Such a People, led by popular TV entertainer Slavi Trifonov.
The opposition Socialist Party is tipped to rank third, followed by the liberal anti-corruption group Democratic Bulgaria and the ethnic Turkish MRF party.
The new centre-left alliance Stand Up! Mafia Out!, which emerged after last year's anti-government protests, is projected to pass the 4 per cent hurdle to enter parliament.
According to political analyst Dimitar Ganev, there are little chances for Borissov to return to office for a fourth term regardless of whether the GERB finishes first in the election because most political groups have rejected the idea of cooperating with the ex-ruling party.
The 12,000 polling stations close at 8 pm. There are 6.7 million eligible voters who are electing 240 lawmakers. Preliminary results are expected around midnight Sunday.
