"Our victory is certain, but we are waiting to see the size of our victory," said Maliki, who has been Iraq's leader since 2006.
Polls opened Wednesday in Iraq's first parliamentary election since US troops withdrew, with Prime Minister Nuri al-Maliki seeking a third term in power amid the country's worst violence in years.
Voters began streaming into election centres nationwide from 7:00 am (0400 GMT), with polling due to end at 6:00 pm (1500 GMT), as more than 9,000 candidates compete for 328 seats in parliament.
Iraqis have a long list of grievances, ranging from poor public services to rampant corruption and soaring unemployment, but the month-long campaign has centred on Maliki's bid for a third term and a dramatic deterioration in security in recent months.
The run-up to the election has seen Baghdad and other major cities swamped in posters and bunting.
Parties have staged rallies and would-be lawmakers have angrily debated on television, though appeals to voters have largely been made on sectarian, ethnic or tribal grounds rather than the issues themselves.
Attacks on polling stations and campaign gatherings in recent days have cast a pall over the vote, and spurred fears that much of the electorate could stay home rather than risk being targeted.