In a final frenzied week of campaigning, Mr Iliescu has appealed to voters to see him as the "father of the nation" and the guarantor of stability and the goals of the December 1989 revolution.
But in many towns he has been jeered by crowds angry about the slow pace of economic reform and widespread poverty and corruption.
Almost seven years after the toppling of Ceausescu, the average monthly wage in Romania is still under $100 (pounds 66). The country lags far behind Poland and Hungary. For many, liberation from Communism and the coming of the free market have brought hardship, and anger is rising towards those deemed responsible.
In the presidential contest, opinion polls predict that Mr Iliescu may just emerge slightly ahead of his two main rivals: Emil Constantinescu, an academic who heads the opposition Democratic Convention (CDR) and Petre Roman, a former prime minister with whom the President once worked in tandem. The second-round run-off is planned to take place in two weeks' time.
The parallel parliamentary poll is almost certain to see a defeat for Mr Iliescu's Party of Social Democracy (PDSR), the reformist successor to Ceausescu's Communist Party.
"The Romanian political establishment faces a major democratic test on Sunday - a transfer of power," declared the independent Adevarul paper in a recent editorial. "Romania is the only East European country where there has been no real transfer of power since 1989."
Mr Iliescu, who emerged from the shadows of the Communist Party to mastermind the coup against Ceausescu, acknowledges that if he scrapes home in the presidential poll he may have to work with a hostile parliament. But after the bitterness of the election campaign, a French-style system of cohabitation would prove a tough challenge.