Prime Minister Anton Rop conceded defeat after preliminary results showed the center-right opposition winning Sunday's parliamentary elections, putting it in power for the first time since Slovenia became independent in 1991.
Janez Jansa's Slovene Democratic Party held 29 percent of the vote -- 6 percentage points ahead of Rop's Liberal Democratic Party -- with just over half the votes counted. About 1.6 million voters were eligible to cast ballots at 3,400 polling places.
"A much-needed political change has come to Slovenia, and we have the program and the people to carry out that change," Jansa told private Pop television.
Rop's center-left party has governed for all but a few months since the former Yugoslav republic gained independence. The party's crowning achievement came earlier this year when the country joined the European Union and NATO.
Two smaller allies of Jansa's party finished fourth and fifth, but it was unclear whether his center-right coalition would garner enough seats in the 90-seat legislature to form a government without having to court fringe groups.
It was not known when final official results would be announced, but the margins were unlikely to change significantly.
Though this country of 2 million people boasts low unemployment, a strong trade balance and steady growth, voters seemed to fear that their voices could be drowned out by the 450 million residents of the 25-nation E.U.
Slovenia became the first Yugoslav republic to declare independence, touching off a 10-day war in 1991.