Nikolic, the deputy chairman of the Radical Party, toned down his firebrand style that had been likened to that of former Serbian leader Slobodan Milosevic. He muted his rhetoric on Kosovo -- then just weeks away from self-declared independence -- and refashioned himself as a smiling, reasonable moderate who could do business with Moscow, Brussels, and Washington alike.
Those days however, are over.
The old, angry Nikolic is back, lashing out with particular vehemence at the European Union, which he recently accused of using false promises to lure Serbs into voting for pro-Western parties in the March 11 early parliamentary elections.
"[Kosovo Prime Minister Hashim] Thaci is expecting to get an agreement with the EU in three months. That's why this agreement [between the EU and Serbia] is a trap," Nikolic said. "The EU is saying, 'Today we sign an agreement with Serbia. Tomorrow with Kosovo. And during this time we'll continue to make Serbia promises about new investments and projects, but only if the Democratic Party wins.'"
Nikolic, who ultimately lost to Democratic Party head Boris Tadic by some 100,000 votes, appears to be taking no chances as the Radicals head into the May 11 ballot.
The vote -- called after Serbia's coalition government collapsed in March amid infighting over Kosovo -- finds the Radicals and other nationalists disavowing ties with the West, snuggling up to Russia, and stoking concerns among Balkan neighbors that an angry, isolationist Belgrade is once again on the ascent.
Although polls show the two major parties -- the Radicals and Tadic's Democrats -- almost neck and neck with roughly 35 percent each, many expect Nikolic will emerge triumphant by sealing a deal with Tadic's former coalition partner, acting Prime Minister Vojislav Kostunica, whose Democratic Party of Serbia (DSS) is currently polling at 12 percent.
Both sides, so far, vehemently deny such a deal has been made. But media reports suggest the plan is the initiative of Radical Party founder and leader Vojislav Seselj, who these days conducts his business from a jail cell in The Hague, where he is on trial for war crimes and crimes against humanity by the International Criminal Tribunal for the Former Yugoslavia.
Such speculation has, predictably, raised hackles in Tadic's camp. But it has also angered members of Kostunica's party, who say any association with the Radicals and Seselj is a political liability.
Still, according to analyst Dejan Vuk Stankovic, in many ways a Radical-DSS partnership is reasonable to expect. The two parties see eye-to-eye on many issues, and have been careful not to criticize each other during the preelection season.
"With or without a [prior] agreement, it's obvious that the two sides have a high level of understanding over two key issues in this campaign -- Serbia's stance toward Kosovo and toward the policy of European integration," Stankovic said. "The Radicals have shown a heightened readiness for cooperation. Because they will be the stronger partner, I believe that their coalition -- if both win a sufficient number of votes -- can easily become a reality in Serbia."
That reality could deal a decisive blow to Belgrade's progress toward EU membership. Despite support among a majority of Serbs for joining the 27-member bloc, many in the political sphere see the issue as inextricably tied to the question of Kosovo -- and therefore impossible to resolve.
Nineteen EU member states have recognized Pristina's independence declaration, which has dulled the integrationist zeal of many Serbs, who are virtually united in their refusal to accept that Kosovo -- a region they see as the historic birthplace of Serbian statehood -- has left, or will ever leave, the fold.
Brussels has attempted to lighten the mood by signing off last week on a Stabilization and Association Agreement (SAA) that marks the first step toward EU membership. This week it upped the ante by offering to waive expensive visa fees for Serbian citizens to travel to 17 EU countries.
Tadic, who signed the agreement together with Deputy Prime Minister Bozidar Djelic, hailed the SAA as a critical step in Serbia's Western integration.
"The signatures for the Stabilization and Association Agreement mark a new page in the history of the Western Balkans," Tadic said. "Once more, I want to point out that Serbia has the right and obligation to defend its integrity and its identity. And Serbia has the full right to secure its European future."
Brussels' gestures, however, may backfire. Kostunica has already sharply criticized the EU and Tadic for signing the SAA, which he characterized as a vote-buying trick played at the expense of Serbs' commitment to Kosovo remaining a part of Serbia. (Kostunica, by contrast, has sought to firm up energy deals with Russia ahead of the election, as a way of demonstrating that Belgrade's true loyalties lie to the East.)
Tadic maintains that signing the SAA does not amount to an acceptance of Kosovo independence. But his move has been interpreted by some Serbs as a betrayal. Local newspapers this week reported that Tadic had received a letter accusing him of "treason" and threatening that he would receive "a bullet in the forehead" for his actions.
Coming just five years after Tadic's mentor, pro-reform Prime Minister Zoran Djindjic, was assassinated in Belgrade, the threat is for many a grim reminder that thuggishness may once again become a prime characteristic of Serbian politics.
That's a worry not only for Tadic, but for Kosovo's ethnic Albanian majority. They have watched nervously as minority Serbs -- located mainly in the northern half of the divided city of Mitrovica -- have drained away from Kosovo's official structures and taken steps to create parallel government structures of their own.
For many Kosovo Serbs, the case has a precedent in Serbian Krajina, a self-proclaimed Serbian entity established within Croatia during the 1990s. Krajina was secured by a Serb paramilitary unit and maintained its own government institutions during its four years of existence. (It was ultimately overrun by Croatian forces; more than 1,500 Serbs were killed in the attack, at least 250,000 more were expelled.)
Paramilitaries have yet to patrol Serb-controlled north Mitrovica; Belgrade has yet to call for the formation of a breakaway Serb state within Kosovo. Marko Jaksic, a Kosovo Serb leader and a member of Kostunica's DSS, has said there is no gain to be had in a comparison with the Krajina Serbs, and that north Mitrovica should rest easy with the assurance that Belgrade is watching over it.
"Serbia has said that Krajina was part of Croatia, but that Kosovo is part of Serbia," Jaksic said. "Kosovo Serbs have rested upon Belgrade because, according to the Serbian Constitution, Kosovo is part of Serbia, and therefore Serbia is obliged to defend those territories."
RFE/RL's South Slavic and Albanian Languages Service contributed to this report