(Bloomberg) -- Croatia’s highest court said President Zoran Milanovic’s abrupt decision to run in next month’s election to become prime minister is “irreconcilable” with his role, a decision the head of state called a “coup” even as he signaled he’d respect the ruling. 

Miroslav Separovic, head of the Constitutional Court in Zagreb, said on Monday that Milanovic can’t campaign in the contest, run on a party list or as a candidate for the premiership without resigning his post as president. Milanovic said on Friday he would step down as head of state only after an election victory on April 17. 

Responding to the court decision hours later, Milanovic signaled that even if he conforms with the campaigning restrictions, he would maintain his ambition to succeed his bitter rival, Prime Minister Andrej Plenkovic, in next month’s contest. 

“This is a coup — they’re trying to obstruct the will of Croatian voters,” Milanovic told a crowd in Vela Luka, a fishing village on the Adriatic coast. “I will be the prime minister, but I won’t tell those illiterate mobsters how I intend to do it.” 

The blunt exchange amounted to a constitutional standoff as the court grapples with a sitting head of state wading into a highly charged election campaign, threatening to call off the ballot altogether if Milanovic doesn’t comply. Croatia’s constitution spells out the role of president as a non-partisan figure tasked with preserving the stability of the country. 

‘A constitutional crisis’

Milanovic endorsed comments made earlier by the leader of his Social Democrats, Pedja Grbin, who said he would now refrain from referring to the president as the party’s candidate — but would “holler” after the election results are tallied next month. 

Croatia’s prime minister isn’t directly elected, but put forward by party majorities in parliament, meaning that Milanovic could receive the mandate whether he campaigns as a candidate on the ballot or not. But the head of the court took issue with the president’s adherence to the constitution.   

“President Milanovic has already violated the constitution with his conduct from Friday to today,” Separovic said. “We are trying to prevent a constitutional crisis.”

Milanovic last week threw open the parliamentary contest by announcing the bid to lead the opposition Social Democrats. A former prime minister who was elected head of state in 2020, Milanovic remains one of the country’s most popular figures. 

A snap poll over the weekend gave Milanovic a slight lead over Plenkovic, whose Croatian Democratic Union, or HDZ, had been well positioned to secure a third term. 

A Milanovic premiership could have repercussions for the European Union as the most recent EU and euro member state shifts on policy. A stalwart supporter of Ukraine under Plenkovic, Croatia could reverse that position with a leader who has been critical of the bloc’s stance against Russia. Milanovic opposed NATO accession for Finland and Sweden and prevented Croatia from hosting officer training for the Ukrainian military. 

The Croatian president has also adopted a barbed political style, attacking his opponents in parliament as well as the courts.  

“After the election, we will deal with this mobster group,” Milanovic told voters on the coast. “There won’t be shooting — there won’t be beating, but we will have a Third Republic.”

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