Vojislav Kostunica may have rallied Serbia's people against Yugoslav President Slobodan Milosevic, but he has failed to keep his coalition government together.
Vojislav Kostunica may join ranks with hardline nationalists
Eight years ago, he was a popular law professor who replaced Milosevic as president of the Federal Republic of Yugoslavia,
He became president of the renamed Serbia and Montenegro and later, prime minister.
The nationalist has taken a strong stance against Western influence on Serbia. He opposed the extradition of Milosevic to The Hague and more recently
has opposed the decision by European Union states to recognise an independent Kosovo.
Political relations at home have also been rocky. As president, his stance on Milosevic's extradition put him at odds with Prime Minister Zoran Djindjic, until the latter's assassination in 2003.
During Mr Kostunica's first term as prime minister (2004 to 2006), he had to rely on Milosevic's weakened Socialists, drawing criticism from former pro-Western allies.
It was also the first sign of his increasingly nationalist stance.
He returned to power in May 2007 with a last minute coalition deal with the pro-Western Democratic Party.
Critics at home have described Mr Kostunica as a "new Milosevic"
He is known for his opposition to Kosovo's independence, focusing on the province's religious and cultural significance and the sanctity of Serbia's territorial integrity.
He has also forged closer ties with Moscow, that has led to speculation that he will
be co-operating with hardline nationalists in the next election.
Mr Kostunica's nationalist convictions have been evident since his youth.
Born in Belgrade in 1944, he was the son of an officer in the pre-war Yugoslav army. He studied law at Belgrade University in the late 1960s and early 1970s.
Anti-communism and nationalism were combined in Mr Kostunica's thinking as far back as 1974 when, as a young academic, he criticised Tito's reshaping of the Yugoslav constitution along the lines of a loose-knit federation.
He believed the federation undermined the position of Serbs who lived outside Serbia, or in Serbia's then newly-autonomous provinces, Kosovo and Vojvodina. He was punished for his criticism by being dismissed from Belgrade University's law faculty.
Mr Kostunica was among the founding members of the Democratic Party but he left in 1992 because he considered it was not sufficiently nationalist. His newly-established Democratic Party of Serbia formed an alliance with the charismatic Vuk Draskovic's conservative Serbian Renewal Movement (SPO).
Mr Kostunica has increased ties with Russia, especially over Kosovo
But just a year later, personal rivalry prompted Mr Kostunica to break with Mr Draskovic. Thereafter, his party remained on the margins of Serbian politics
When most of Serbia's opposition parties came together to form the "Zajedno" alliance in 1996, Mr Kostunica never became more than a semi-detached member of the coalition. He stayed away from the mass public protests in late 1996 and early 1997 which helped to force President Milosevic to concede the opposition's unprecedented election victories in Serbia's major towns.
His failure to line up behind the "Zajedno" coalition appeared to cost Mr Kostunica considerable political support.
But the revival of Serb nationalism with the escalation of the Kosovo conflict gave Mr Kostunica another chance - particularly because other better-known opposition leaders had lost public backing through their public disputes.
Analysts say these qualities of consistency and standing by his principles over the years explain, at least in part, why so many Serbs were prepared to support him in his bid oust Milosevic.
And, correspondents say they did so in spite of the fact that Mr Kostunica lacked the charisma or popular appeal of other opposition leaders.