Boris Tadic, who championed Serbia's bid to become a member of the European Union, was leading the polls against former right-wing extremist Tomislav Nikolic, days ahead of the key presidential runoff on Sunday. Tadic was half a percent ahead of Nikolic in the first round of voting on May 6, while Nikolic's Progressive Party won the most votes for parliament...The outcome is critical for Serbia's hopes of moving toward EU membership and shaking off its image as an international pariah from the 1990s' Balkans wars under late strongman Slobodan Milosevic. Tadic led Serbia's EU bid when it became a candidate for entry in March, following the long-awaited arrest of Mladic and former Bosnian Serb leader Radovan Karadzic. His government turned the two over to a U.N. tribunal in the Netherlands to face genocide charges for their role in the 1992-95 Bosnian war...Tadic handed over Mladic last year, after police tracked him down to a cousin's house north of Belgrade. The former general is accused of orchestrating the slaughter of 8,000 Muslim men and boys at Srebrenica, Europe's worst massacre since World War II...As Mladic's genocide trial started in the Hague tribunal this week, it caused no stir in Serbia, with media only carrying brief reports from the courtroom. Mladic was largely ignored in campaigning by the presidential candidates, who focused on economic problems instead. "That (war crimes) is no longer a topic," said Natasa Kandic, a leading human rights activist in Serbia. She added that "Mladic was the topic when Serbia was under pressure to arrest him." Tadic has built his presidential bid around his pro-EU policies, but his biggest problem remains the economic downturn and corruption within the ruling elite. Faced with the global financial crisis, which slowed down much needed foreign investments, Tadic's government has seen massive job losses and plummeting living standards. Nikolic, who narrowly lost two earlier presidential votes against Tadic, claims to have shifted from being staunchly anti-Western to pro-EU, and says that he wants Serbia both "in the West and the East." Nikolic has close ties with Russia and has even in the past envisaged Serbia as a Russian province. Nikolic's populism has struck a chord with voters, who warmed to his criticism of widespread social injustice and corruption in Serbia and promises of jobs, financial security and billions of dollars in foreign investment. A pre-election survey by Ipsos Strategic Marketing agency published last week, gave Tadic 52 percent over Nikolic's 48...Tensions soared last week when Nikolic accused Tadic's camp of election fraud during the general vote on May 6...If he wins, Tadic will have a chance to push forward Serbia's EU bid and try to win a date for opening accession talks. The new government also must introduce painful economic reform and move to root out corruption in order to move closer to EU membership. Tadic has also overseen a more conciliatory stance toward Serbia's neighbors and former Balkan war foes, including Kosovo, the former province which split in 2008. Nikolic has said he would abandon the EU plan if it means that Serbia must give up the claim on Kosovo, and he has forged an alliance with the staunchly anti-EU party of former premier Vojislav Kostunica. In a pre-election debate on Wednesday, Nikolic urged voters to "punish Tadic for unfulfilled promises." "Sunday is our last chance for change!" he said on state television. Tadic called for stability so that Serbia can move forward in its EU bid. He accused Nikolic of fueling instability and possible violence with his allegations of vote rigging. "May 20 will be a referendum over which way Serbia will take, whether it will go straight to the EU or take a turn or two," Tadic said. "I believe that the only way forward for Serbia is toward the European Union."