Serbian President Boris Tadic is stepping down ahead of presidential and parliamentary elections on May 6, dpa quoted broadcaster B92 as reporting Tuesday. His official functions will be carried out in the interim by parliamentary president Slavica Dukic Dejanovic, who is also due to formally announce the elections on Wednesday, the television station reported. Tadic's full presidential term would have continued until the end of the year. Election observers said that the move was aimed at boosting the chances of the ruling Democratic Party (DS), which Tadic heads. The party has slipped in recent surveys, which showed the nationalist opposition as favourites. Tadic and the DS are being blamed for economic and social problems in Serbia. The opposition Serbian Progressive Party (SNS) is the clear election favourite according to opinion polls. Their leader, Tomislav Nikolic, is challenging Tadic for the presidency.