IT IS easy to imagine Milo Djukanovic, the prime minister of Montenegro, whistling “Leader of the pack” on his way to work. The undisputed survivor of Balkan politics, he has led his country in one job or another since 1989, making him perhaps Europe’s most successful statesman. And he is still only 51. In 2006 he steered Montenegro towards independence from the rump union with Serbia. Since Croatia joined the European Union in July his country, which began accession talks last year, has been in pole position to follow, stealing a march on both Serbia and the four other aspiring Balkan countries.Yet Mr Djukanovic faces new problems at home. His junior partners, the Social Democrats (SDP), are acting like an opposition party; parliament has begun to exercise more power; and EU officials are demanding more action against crime and corruption. This is reducing Mr Djukanovic’s room for manoeuvre, says Daliborka Uljarevic, a leading civic activist, and that “is making him nervous”.It also means that the political landscape is changing, even if only slowly. No government of Montenegro has ever been changed through the ballot box, but such an outcome may no longer be…