By Daniel SerwerNot much, in the first instance. It has now been a long time since a president of the United States regarded the Balkans as a priority. A region that in the 1990s was the object of two US military interventions (in Bosnia and Kosovo) and NATO deployments has dribbled its way down the list of priorities and now rests no higher on most days than a deputy assistant secretary in the State Department.That’s not a bad thing: democracy and statebuilding in the Western Balkans has been relatively successful, with Slovenia, Croatia and Albania now NATO members and Montenegro in the accession process.Slovenia and Croatia are also EU members and all the other countries of the region are pointed in that direction, each at its own pace.But the Westernization process in the Western Balkans is still not complete, has slowed recently, and could be curtailed or even reversed during the Trump administration. Bosnia is suffering attacks on its constitutional legitimacy, rooted in the Dayton peace accords of 1995, from the President of the relatively autonomous 49% of the country known as Republika Srpska.Macedonia is stalled due to internal strife and Greece’s refusal to accept is name.Kosovo started its existence as a sovereign state well behind the others and likewise suffers internal strife and continuing problems due to Serbia’s non-recognition.All the Balkan countries are suffering a Russian soft power assault on their media and institutions.If the new president is inclined to accept a Russian sphere of influence in the Balkans, the consequences for the region’s relatively new democracies could be dramatic. Montenegro’s NATO accession depends on ratification in the US Senate. Progress in Bosnia will require the EU and the US to act in tandem to promote political and economic reforms.Improved relations between Kosovo and Serbia likewise depend on concerted action Brussels and Washington, as will resolution of Macedonia’s internal and external problems. Just easing up on these ongoing efforts could doom them to failure.But worse could be in store. Trump wants to improve American relations with Russia and may be tempted to concede items of value to get them. If, for example, he were to accept Russian annexation of Crimea, that alone could set off a series of ethnically based partitions not only in Ukraine but also elsewhere: in Georgia, Moldova, Bosnia, Kosovo, and Macedonia.It would be truly miraculous if such a chain of partitions were to occur peacefully. It is far more likely that it would entail instability, ethnic cleansing, redrawing of borders, and war. White nationalists like Steve Bannon, Trump’s chief long-term strategist, will no doubt be telling the new president that ethnic partition is natural or inevitable and not such a bad thing after all.What this amounts to in the Balkans is an assault on the post-war order established in the late 1990s as the most recent Balkan wars came to an end. It wasn’t an entirely liberal democratic order, as ethnic identity and group rights have remained an important dimension of organized political life virtually everywhere in the region.But it was an order based on aspirations to EU and for some NATO membership that involved establishing independent judiciaries, relatively free media, representative legislative bodies, and peaceful resolution of disputes.Upsetting this order in favor of ethnic separation and illiberal autocracies with territorial pretensions would be perilous: this is a part of the world involved in two world wars, in addition to its own post-Cold War conflicts arising from the breakup of former Yugoslavia.I don’t expect Steve Bannon or John Bolton to worry about that, but I do hope that more pragmatic Republicans like Senate Foreign Relations Committee Chair Corker or outgoing New Hampshire Senator Ayotte, both of whom are rumored for cabinet positions, to understand that the Balkan wars of the 1990s and the subsequent peace were a bipartisan effort, with support led as much by Republican Senator Dole as anyone else. Preserving that bipartisan legacy of peace and increasing prosperity is important, even if the region no longer attracts high level attention.