SOFIA, Bulgaria (AP) — Bulgaria, the EU’s poorest country, holds presidential and mayoral elections on Sunday, and many see them as a test of the nation’s political stability at a time of economic crisis.

Some observers have said that one of the biggest tests may be to prevent impoverished Bulgarians from selling their votes in a country with widespread crime and corruption.

Polls have indicated that none of the 18 presidential candidates is likely to win Sunday’s election by getting more than 50 percent of the vote, and that a runoff will be required on Oct. 30.

In Bulgaria, presidents have no executive powers, but they can veto legislation approved by Parliament. Bulgaria’s current socialist president, Georgi Parvanov, has served two five-year terms and was barred from seeking re-election.

The front-runner to replace him is Construction Minister Rosen Plevneliev, with about 30 percent of the vote, according to recent polls. Plevneliev is a member of the governing GERB party of Prime Minister Boiko Borisov.

Two other presidential candidates — Ivailo Kalfin, a former foreign minister of the opposition Socialist Party, and independent Meglena Kuneva, a former European Union commissioner — are expected to finish second and third.

One Bulgarian citizen, 24-year-old construction worker Yordan Balev, said he plans to vote for one of the least likely candidates to win: rock singer Svetlyo Vitkov. "I have no illusions that he can win, but we should show politicians that people are fed up with their hollow promises," Balev said in an interview.

A victory by Plevneliev could increase the chances of Borisov’s minority center-right government to push ahead with its painful economic reforms in a country with an average monthly salary of (euro) 340 ($470) and 11.7 percent unemployment. One labor union has estimated that 20 percent of Bulgarian families are impoverished.

The eurozone debt crisis has reduced demand for exports from this Balkan country, and the European Bank for Reconstruction and Development recently revised its growth forecast for Bulgaria in 2012 to 2.3 percent, down from its previous prediction of 3.7 percent.

Bulgaria’s economic woes have been at the heart of the election campaign, with opposition contenders accusing the incumbents of stalling with key reforms.

Rooting out corruption and organized crime has been a key goal of Borisov’s government, but the challenges it has faced during its two years in power were evident recently when the EU refused to include Bulgaria in its passport-free Schengen travel zone due what it called widespread graft.

The election campaign has been marred by several protests against Bulgaria’s Roma minority, including one where riots saw residents of a small village set fire to houses and cars owned by a local Roma leader.

During the campaign, a makeshift bomb also exploded under the car of a popular Bulgarian journalist who has been a fierce critic of the government. No one was injured in the blast.

International observers have voiced concern about the fairness of Sunday’s elections, which also will chose mayors in cities across the country, including Sofia, the capital.

"There are fears about large-scale vote buying and manipulations in the counting of the ballots," the OSCE monitoring team said in a report on Wednesday.

A separate report by the graft watchdog Transparency International predicted that as many as 20 percent of Bulgarian voters would try to sell their ballots.