The New York Times has a simple narrative for you:

Nine candidates were vying for the presidency, but only two were considered serious contenders: the pro-Western incumbent, Mr. Tadic, and his pro-Russian nationalist challenger, Mr. Nikolic. The presidency is formally a ceremonial post in Serbia. But during Mr. Milosevic’s autocratic government in the 1990s, when he virtually ruled alone, it gained in importance and influence.

Mr. Tadic, a telegenic and soft-spoken moderate who is supported by a majority of European leaders, advocates Western-style reforms and integration into the European Union, after more than a decade of isolation and wars under Mr. Milosevic.

…

Mr. Nikolic, a former ally of Mr. Milosevic, has sought to evoke Serbs’ nationalist pride by playing on their growing frustration over American and European Union backing for Kosovo independence. Analysts say a victory by Mr. Nikolic would probably bury Serbia’s pro-European aspirations, push the country back into political isolation and undermine its economic prospects.

Nonsense on stilts. Tadic has been playing the nationalist card as well, edging towards Russia, going along with Prime Minister Kostunica’s dirty games—all in hopes of taking some votes away from the Radicals and Nikolic. He is a cowardly politician who’s made some bad decisions during the past few years, and he will likely lose for it.

Furthermore, this is not the result of “growing frustration over American and European Union backing for Kosovo independence” as the Times would have it. The real story here is that there is a very large percentage of Serbs, quite possibly a plurality, who have not renounced their recent history and for whom Kosovo and Bosnia are still open questions. These are the same forces that brought Milosevic to power and who supported him through three disastrous wars. The Balkans will not be peaceful until Serbia goes through some sort of catharsis and relegates these ideas to its fringes.