Turkey’s fiercely contested presidential election appears likely to go to a second round after President Recep Tayyip Erdogan failed to secure 50% of votes cast to decisively extend his 20-year rule, CNN reports.

The high stakes election will ultimately decide the fate of a key NATO ally and regional power broker at a time when Russia’s invasion of Ukraine has plunged much of the world into uncertainty.

The mood noticeably darkened at the headquarters of Erdogan’s Justice and Development Party (AK Party) in Istanbul on Sunday evening as his early lead slipped away.

With 97.95% of votes counted, state-run Anadolu news agency reported Erdogan had 49.34% of votes, compared to 44.99% for his main opponent, Kemal Kilicdaroglu – meaning neither could claim an outright win.

The third candidate, Sinan Ogan, received 5.28% of votes, according to Anadolu, raising the possibility he could be a kingmaker in a runoff. He tweeted that a second vote is “quite possible,” and that “Turkish nationalists and Ataturkists are in a key position for this election.”

Kilicdaroglu welcomed the prospect of a runoff vote and said his party would triumph.

“If our nation says second round, we gladly accept it. We will absolutely win this election in the second round. Everyone will see that,” he said, of the runoff, slated for May 28.

Sunday’s race poses the biggest challenge yet to Turkey’s strongman leader Erdogan, who faced economic headwinds and criticism that the impact of the devastating February 6 earthquake.

For the first time, Turkey’s factious opposition coalesced around a single candidate, Kilicdaroglu, who represents an election coalition of six opposition parties.

Before the vote, analysts predicted that Erdogan would not give up power without a struggle – and that even if Kilicdaroglu managed to pull ahead, it was possible the numbers could be contested.

The outcome of the make-or-break vote is also being closely watched internationally, especially in Moscow and Europe.

Turkey, a NATO member that has the alliance’s second-largest army, has strengthened its ties with Russia in recent years. In 2019, it even bought weapons from the country in defiance of the US.

More recently Erdogan has raised eyebrows in the West by continuing to maintain close ties with Russia as it continues its Ukraine onslaught, and has caused a headache for NATO’s expansion plans by stalling the membership of Finland and Sweden.