Rome's conservative mayor was trailing badly in his re-election bid Monday and appeared headed toward a runoff with a center-left challenger, according to projections and partial vote counting.

The Italian capital was the only big city up for grabs among mayoral races in around 500 towns. The two-day vote was marked by a sharp drop in turnout nationwide — the latest sign of Italians' disenchantment with politicians who have been unable to steer the eurozone's third-largest economy out of recession.

Rome Mayor Gianni Alemanno, who only received tepid support from his conservative party leader Silvio Berlusconi, had about 29 percent of the vote, nearly 15 percentage points behind center-left challenger Ignazio Marino, according to projections on sample ballots by the Tecne polling company.

The next contenders were far behind. The Tecne projections had a 2 percent margin of error.

The actual vote count, with about 50 percent of Rome's polling stations reporting, was in line with those projections.

Alemanno acknowledged his second-place finish but vowed to prevail in the runoff in two weeks.

Marino attributed his showing to Roman disappointment with Alemanno's tenure in City Hall, which included a job- patronage scandal in some municipal agencies and repeated mass transport strikes.

The vote in Rome carried special significance since it was seen as a test of former premier Berlusconi's political influence amid his judicial woes, including a sex-for-hire trial in Milan and a recent tax-fraud conviction.

Berlusconi's speech last week for Alemanno drew an embarrassingly small crowd in a city of more than 2 million voters.

Berlusconi's center-right People of Freedom party and Marino's center-left Democratic Party are the two main partners in the national government, a tense coalition of political enemies who united to break two months of political deadlock after an inconclusive February vote.

The candidate for the anti-establishment 5-Star Movement, Marcello De Vito, appeared to be finishing far back, according to projections.

"We'll be a tough opposition" force in City Hall, De Vito told reporters.

Alemanno brushed off the significance of his second-place showing.

"A runoff is a whole new ball game," the mayor told reporters.

Rome's turnout plunged to about 54 percent from some 74 percent in the last 2008 race. Nationwide turnout also dropped sharply, from 77.2 percent in 2008 to 62.4 percent in this week's balloting.

"A lot of people are just fed up," said James Walston, a political science professor at the American University of Rome.