The shape-shifting president of Montenegro, Milo Djukanovic, Europe’s longest-serving elected leader, lost a re-election bid on Sunday, according to provisional official results, raising hopes across the Balkans of a long-awaited end to a political era stamped by the Yugoslav wars of the early 1990s.
The vote on Sunday was a runoff between the two top finishers among seven candidates competing in a first round last month. Mr. Djukanovic, 61, conceded defeat late Sunday to Jakov Milatovic, 36, an Oxford-educated economist who campaigned on pledges to root out corruption and organized crime.
Mr. Milatovic won decisively with about 60 percent of the vote, with 70 percent counted as of Sunday night.
Mr. Djukanovic said he respected the outcome of the vote and wished Mr. Milatovic success, adding, “If he is successful, it means that Montenegro can be a successful country.”
Mr. Milatovic, endorsed by most of the losing candidates in the first round, had been expected to win, but Mr. Djukanovic, a consummate political survivor, had dominated Montenegro for so long — he served four terms as prime minister and two as president — that his defeat still caused a sensation.
“Tonight is the night we have been waiting for for more than 30 years,” Mr. Milatovic told supporters in Podgorica, the Montenegrin capital. “We said goodbye to crime and corruption. This is a historic day for everyone.”
Mr. Djukanovic has been dogged throughout his career by accusations of links to organized crime, which he has strenuously denied.
The defeat of a leader who began his political career in the former Yugoslavia lifted the spirits of opposition groups elsewhere in the Balkans, particularly in neighboring Serbia, whose own entrenched veteran leader, Aleksandar Vucic, also got his start in Yugoslavia and has been a fixture of Serbian politics for decades.
“We hope that this victory will be a clear signal to everyone that the previous policies of division and conflict are dying because the entire region needs new people and new energy,” the Serbian opposition party Zajedno said in a statement welcoming Mr. Milatovic’s victory.
Yugoslavia, a federation of republics, dissolved in 1992, but unlike, Slovenia, Croatia, Bosnia and Macedonia, which had all declared independence, Montenegro and Serbia formed a new federal state called Serbia-Montenegro. That entity, shaky from the start, fell apart after Montenegro declared independence in 2006.
Mr. Djukanovic first came to power in 1991 as prime minister of Montenegro, then still part of Yugoslavia. Initially a close ally of Slobodan Milosevic, Serbia’s Russia-friendly strongman leader, he later shifted his allegiances to the United States, securing Montenegro’s entry to NATO in 2017 despite widespread public hostility to a military alliance that had bombed the country in 1999.
Mr. Djukanovic also sought membership in the European Union, but that effort, which began in 2008, stumbled largely because of Montenegro’s reputation for sheltering criminals.
Mr. Milatovic vowed on Sunday to get the country into the bloc before the end of his five-year term as president.
A political novice, Mr. Milatovic ran as a candidate for the newly formed party Europe Now and promised to shed Montenegro’s unsavory image. He accused Mr. Djukanovic of turning the country into the “Colombia of the Balkans,” a reference to Montenegro’s role as a hub for smuggling cigarettes and other contraband.
Mr. Djukanovic was close to Russia in the 1990s and 2000s, when Montenegro opened its doors to a flood of investment from Russia and became a popular holiday destination for Russians. But he later threw his lot in with the West, accusing Russia of orchestrating what his officials said was a botched 2016 coup aimed at torpedoing the country’s NATO membership.
He also reached out to China, sealing a deal with that country’s state companies for the construction of a “highway to nowhere” that cost nearly $1 billion and severely strained Montenegro’s finances.
Mr. Djukanovic tried to paint Mr. Milatovic, his electoral rival, as a stalking horse for Serb interests, citing his endorsement by pro-Serb politicians. But that was a hard sell given Mr. Milatovic’s previous career with Deutsche Bank and the European Bank for Reconstruction and Development, and the incumbent’s own long record of flip-flops and questionable dealings.
Alisa Dogramadzieva contributed reporting.