The results highlighted deep divisions between Poland's cities, which have many liberal voters, and the country's rural heartland, which remains largely supportive of Law and Justice despite accusations it has taken an authoritarian direction and its conflicts with the European Union.
Runoff voting is taking place in 649 municipalities. Results from exit polls conducted during the runoff races are expected to be released when polling stations close Sunday night. Official returns are not expected until Monday at the earliest.
The centrist opposition is favored to win in Krakow and Gdansk The local elections kick off a string of votes setting Poland's course, including the May election choosing European Parliament representatives, the national parliament vote in fall 2019 and a presidential election in the spring of 2020.
Law and Justice won 34 percent of the total regional assembly votes two weeks ago, and the opposition coalition nearly 28 percent. One of the primary jobs of the assemblies is choosing how to spend EU subsidies.
If the conservative ruling party maintains the level of support it received two weeks ago, it would appear to be well-poised to remain in power after the 2019 national elections, but without the supermajority in parliament it has been seeking to pursue constitutional amendments.