SOFIA, Bulgaria (AP) — Bulgarians headed to the polls on Sunday to elect their next president in a campaign centered on growing economic hardship and drone attacks on Black Sea shipping.

The vote will also be the first major test for the Moscow-friendly Progressive Bulgaria party of Prime Minister Rumen Radev after its triumph in parliamentary elections in April.

Despite a record number of candidates, the race is expected to be decided in a runoff between incumbent President Iliana Yotova, backed by Radev’s party, and former caretaker Prime Minister Andrey Gyurov, who is backed by pro-Western opposition parties.

The campaign has focused heavily on Russia’s invasion of Ukraine and the widening hostilities in the Black Sea, where recent drone attacks on commercial vessels off Bulgaria’s coast have heightened security concerns in the European Union and NATO member country.

The strikes have raised concerns over Russia’s intentions to escalate the conflict and prompted the government to ask Bulgaria's partners for assistance to strengthen its maritime security.

Candidates have also sought to address public anxiety over rising energy prices and inflation, as many families, particularly in rural areas, struggle to make ends meet.

Polling stations opened at 7 a.m., and are to close at 8 p.m., after which initial exit polls will be announced. Preliminary results are expected on Monday.

The election will likely go into a runoff as none of the 27 candidates is expected to win outright on Sunday. Turnout must be above 50% of 6.6 million registered voters, and the winner needs a majority of votes.

Sunday’s turnout has been projected for less than 40%, which would mean a Nov. 1 runoff.