(ANSA-AFP) - ZAGREB, APR 16 - Croatia heads to the polls on Wednesday for parliamentary elections that have centred around a bitter fight between the country's longtime rivals -- Prime Minister Andrej Plenkovic and President Zoran Milanovic. The showdown comes as Croatia grapples with widespread corruption, a chronic labour shortage, the highest inflation rate in the eurozone and persistent illegal migration along its borders. For months, Plenkovic and his ruling Croatian Democratic Union (HDZ) party looked poised to score an easy win and secure his third term as premier. But in March, Milanovic shocked the nation by saying he would challenge the prime minister. "A quite predictable vote turned into an uncertain battle," political analyst Tihomir Cipek told AFP. Milanovic, whose presidential term expires in January, is backed by the Social Democrats Party (SDP) and says he wants to create a "better and more just country". Milanovic has targeted in particular Plenkovic's recent appointment of a high-ranking judge as Croatia's new state attorney general. The appointment sparked street protesters over the judge's alleged corrupt dealings. Adding to the race's drama, Croatia's top court barred Milanovic from running, since the presidency is largely a ceremonial office for a person without a political affiliation. It said he would have to resign from his post first. But Milanovic has refused and continued to crisscross the country in recent weeks campaigning against the HDZ. If the SDP and its allies are able to win enough seats in the 151-seat assembly, Milanovic could then resign and be named prime minister designate -- in what would be an unprecedented move in Croatia. For now the HDZ continues to enjoy a steady lead in opinion polls, with around 30 percent of voter support compared to 20 percent for the SDP. (ANSA-AFP).