The opposition's candidate, Ivo Josipovic, convincingly won Sunday's Croatian presidential election, pledging to help the government's efforts to complete European Union membership talks and join the bloc in 2012.
Josipovic, a law expert and classical music composer who is relatively inexperienced in high politics, won 60.3 percent of the votes, the state electoral commission said early on Monday.
He will be Croatia's third president since its 1991 independence from Yugoslavia.
Populist Zagreb mayor Milan Bandic, backed by the church and more conservative voters, mustered 39.7 percent of votes as an independent candidate. He was expelled from the Social Democrats for insisting on running for president against the party's will.
Josipovic promised to back Prime Minister Jadranka Kosor's drive to implement reforms and fight widespread corruption, required by Brussels to wind up EU accession talks this year.
"I strongly believe that we all want a better Croatia with more justice, that we want a country where work is paid for and crime is punished," Josipovic said, to the cheers of his supporters.
The ruling conservative HDZ party's candidate did not make it to the runoff but Kosor, who took over in July and kick-started the new anti-corruption drive, remains the country's most popular politician.
"I think we could say Croatia got a sort of a 'dream team' with Kosor and Josipovic, but she must continue in the same vein and he must deliver on his election promises," said Zeljko Trkanjec, political analyst and editor at Jutarnji List daily.
The HDZ last week expelled Kosor's predecessor, Ivo Sanader, after he announced a political comeback with a stinging attack on the party leadership and the government. Kosor later said she felt stronger than ever and determined to press on with reforms.
In his campaign, Josipovic offered "reforms, a fight against corruption and the return of integrity to politics", which analysts and diplomats said was likely to boost the government's efforts in the final stages of EU negotiations.
"They could function great together and that will help Croatia become a country with a real rule of law, which is the basic precondition for EU membership," Trkanjec said.
Josipovic will succeed veteran reformer Stjepan Mesic, whose second five-year term ends in February, and will have limited powers over foreign policy, defence and the intelligence services but none over the economy or legislation.