Voters in Finland will cast ballots on Sunday in a presidential election that comes as NATO’s newest member faces the threat of an antagonistic Russia.

The election, which is expected to require a second round of voting, is for Finland’s first new head of state in 12 years. The country’s wildly popular president, Sauli Niinistö, has served two terms and is ineligible to run again.

Seen as a steadying force, Mr. Niinistö is considered the person most responsible for getting Finland into the NATO alliance, leaving whomever assumes the presidency with big shoes to fill.

From a field of nine candidates, the latest polls show two front-runners: Alexander Stubb and Pekka Haavisto. Both are familiar faces with strong foreign policy credentials.

Results in Sunday’s election are expected later Sunday. If no candidate receives more than half of the vote, a runoff election will be held on Feb. 11 between the top two first-round finishers.

While most European presidents occupy largely ceremonial roles, Finland’s drives foreign policy and serves as the commander in chief. That helped catapult Mr. Niinistö to global prominence after Russia’s invasion of Ukraine in February 2022 — and cemented his approval rating, which exceeds 90 percent.