Serbia result could strengthen stability
Tomislav Nikolic's defeat of Boris Tadic, who has held the Serbian presidency for the past eight years, is a second heavy blow for Mr Tadic's Democratic Party, after its poor showing in parliamentary elections earlier this month.
The Democratic Party has dominated Serbian politics since it led an opposition alliance to overthrow Slobodan Milosevic in October 2000.
But now, the voters have chosen to punish the Democrats, and Boris Tadic personally, for the poor state of the Serbian economy, and a widely held public perception that corruption is rife.
In the parliamentary election, the Democrats won only 23%.
Tomislav Nikolic, a 60-year-old populist who rose to prominence as a radical nationalist, comes across as a smiling, grandfatherly figure, a man who enjoys making plum brandy and walking in the woods in the Serbian heartlands.
Whatever else, this result will mean a change in style at the top of Serbian politics.
Boris Tadic was a suave, English-speaking leader who turned the nominally figurehead position of president into the real power in the land - largely with a series of relatively weak prime ministers.
But the strong showing of the Serbian Socialist Party two weeks ago in the parliamentary election - they came third to Mr Nikolic's Progressive Party and Mr Tadic's Democrats - will make them kingmakers in the next government.
They have already reached a tentative agreement with the Democrats, to form the core of the next coalition, even though the Progressives won the most seats.
The Socialist leader, Ivica Dacic, said on Sunday night that the presidential election result would not change that agreement.
"If Nikolic wins, and Serbia has a president from a different political stripe to the government, that may make domestic politics more complicated, but should not be a major problem when it comes to EU integration," Tim Judah, author and commentator on Serbia, told the BBC before the run-off.
"Serbia will not turn away from the European path," Mr Nikolic announced in his victory speech - a message aimed as much at European capitals, as at a domestic audience.
Under Boris Tadic, Serbia arrested and extradited the last three alleged war criminals from Milosevic's wars to the Hague Tribunal - Radovan Karadzic, Ratko Mladic and Goran Hadzic.
Mr Tadic also won EU candidate status for Serbia, and achieved a breakthrough on relations with Kosovo, according to which Serbia does not recognise the former breakaway province, but tolerates her presence at international meetings, and cooperates with her to solve basic issues in neighbourly relations.
Neighbouring Croatia is due to join the EU next year. A tentative date for Serbia is 2020.
Turn towards centre
Mr Nikolic's ability to take most of the former Radical Party voters to the Progressive Party he founded in 2008, despite a sharp turn towards the political centre, has been the cornerstone of his success.
Two weeks ago, Serbs voted for the status quo - a continuation of the Democrats-Socialist Party led coalition.
What was new in the result then was the strong showing of the Socialists, who doubled their vote and number of seats, and can largely dictate terms to the wounded Democrats.
Interestingly, in the presidential election, a vote for Mr Nikolic was a vote for change.
With turnout at barely 45%, disgruntled voters who supported the Democrats and a host of smaller parties who together swept former Socialist leader Slobodan Milosevic from power in October 2000, voiced their discontent by staying at home.
Two weeks ago, a growing number also spoilt their ballots - a growing trend among liberal-minded youth at Serbian elections. Mr Nikolic can command a much more loyal electorate.
If the new government is formed soon, and the transition from Mr Tadic to Mr Nikolic takes place smoothly, Serbia could win wider recognition as a factor of stability in a Balkan region in which Greece has turned into the main country radiating instability - a very different picture from the 1990s.