Leading article: A fateful vote that may dash hopes of peace in the Balkans

Slobodan Milosevic must be smirking in his grave. Almost a decade after street protests toppled the late dictator of Serbia and Balkan warmonger, his political heirs have come within a whisker of regaining power in Belgrade.

Of course, things have changed since the days of Milosevic's ascendancy, when the Serb-controlled Yugoslav Army and its proxies had the power – and used it – to devastate swaths of the Balkans, bombing Dubrovnik, besieging Vukovar and sending 100,000 or so Bosnians to an early grave.

Serbia today is a much-reduced force, economically and militarily, and even if the hard-line nationalist Radical party turns out to have won yesterday's general election, the Balkans is unlikely to revisit the nightmarish scenes of the 1990s.

That doesn't mean we can afford to turn a blind eye to the general election, however. A nationalist-run Serbia has the potential to create a great deal of mischief, not for only its neighbours but also for the European Union and Nato.

For a start, a Radical-run Belgrade would be hell-bent on causing maximum chaos in Kosovo. Bitterly opposed to the independence of the former Serbian province, which they maintain is the Serbs' "Jerusalem", they will do what they can to inflame tensions there and provoke clashes. Whatever other unwelcome side-effects this development might have, it directly implicates Britain, because our troops still form part of the Nato peacekeeping mission in Kosovo.

Second, the Radicals would turn their attention to Serbia's still-fragile neighbour Bosnia. A traditional target of Serbian nationalist aspirations and home to a large and restive ethnic Serbian community, Bosnia could quickly unravel with a little encouragement from Belgrade.

Finally, the Radicals would inject new energy into Serbia's existing alliance with Russia, quite possibly inviting the Kremlin to set up military bases in the country. If that happened, it would effectively wreck the joint strategy of the EU and Nato towards the Balkans, which is predicated on the idea that local hostilities and ethnic disputes can be best contained, or "frozen", if the entire region is more or less simultaneously locked into key Western institutions.

As it is, we could see the region split into a larger pro-Western and a smaller pro -Russian bloc. This would be a dismal scenario, marking a return to the bad old days when the Balkans was a plaything for rival big powers. Regional trade would wither, putting the brakes on economic recovery and a rise in living standards – the only guarantors of long-term stability. The fires of nationalism would be rekindled everywhere.

Sadly, there is little outsiders can do to persuade Serbs that this is not the right way to go. Angry about Kosovo's secession, consumed with self-pity over the trials of Serbs at the Hague war crimes tribunal and disappointed with the economic results of the past few years, many Serbs put their faith in simplistic slogans about "standing up to the West" and turning the country towards their Orthodox big brothers in Russia.

The EU has already offered a stability agreement with Serbia, the first step towards eventual accession. To do more risks alienating Serbia's neighbours, several of which – such as Macedonia – have exceeded Serbia in satisfying EU accession criteria.

So we have to watch and wait for the outcome of what will probably be a tortuous period of horse-trading after the votes are counted. If the pro-Western forces under Boris Tadic win, we can breathe a sigh of relief. If not, we must brace ourselves for the worst.

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