Georgia ? Serbia’s pro-Western president declared victory in Sunday’s parliamentary elections – a stunning upset over ultranationalists who tried to exploit anger over Kosovo’s independence. But his rivals vowed to fight on, and it was unclear whether he could stave off their challenge.

“This is a great day for Serbia,” Boris Tadic proclaimed after an independent monitoring group that carried out a parallel vote count nationwide said his bloc won 39 percent – about 10 percent more than the ultranationalist Serbian Radical Party.

Tadic, however, acknowledged his nationalist rivals could still team up against his Coalition for a European Serbia and try to form Serbia’s next government. Any alliance that can muster a simple 126-seat majority in the 250-seat parliament can govern, and nationalists indicated they would mount a challenge.

Although Tadic’s coalition appeared assured of 103 seats, the Radicals were poised to get 76 seats. If they joined forces with Prime Minister Vojislav Kostunica’s conservative coalition, with 30 seats, and the Socialist Party of the late Serbian strongman Slobodan Milosevic, with 21, the combined strength would be 127 seats.