Warsaw, Poland CNN  — 

Poland’s incumbent President Andrzej Duda declared victory in the country’s presidential election Sunday, but his opponent refused to accept defeat, saying exit polls show the election is still too close to call.

Duda, backed by the nationalist ruling Law and Justice (PiS) party, won with 51.21% of the vote, the country’s election committee said Monday. The more liberal Warsaw mayor Rafal Trzaskowski, of the center-right opposition Civic Platform party (PO), garnered 48.79%.

His victory will be seen by PiS as a validation of the populist policies it has pursued since coming to power in 2015. Critics worry the win gives the government a blank check to continue its controversial reforms, including the reshaping of the judiciary.

Voter turnout was more than 68%, according to the committee, the highest Poland has seen in 25 years for a presidential poll.

Duda initially declared victory on Sunday, but the Warsaw mayor refused to accept defeat, saying exit polls showed the election was still too close to call. By Monday morning, more than 99% of the votes had been counted, and the election committee’s chairman said any additional votes would not change the outcome.

Incumbent Andrzej Duda, left, faced challenger Rafal Trzaskowski.

Election issues

During campaigning, Duda sought to mobilize his more conservative, largely rural base with appeals to traditional Catholic values and a promise to maintain popular social welfare policies, such as a child allowance and lower pension age.