Exit polls showed Komorowski with a slight edge over Jaroslaw Kaczynski, who essentially conceded defeat in the presidential runoff by declaring before supporters, "I congratulate the winner." Exit polls have a small margin of error, and official results are not expected until Monday.
Komorowski addressed a jubilant crowd of party members in Warsaw. He didn't formally claim victory, noting that the votes were still being counted, but expressed optimism that he would be the next president.
Both presidential candidates are former anti-communist activists with conservative, Roman Catholic upbringings. Yet they differ sharply on key issues, primarily the role of the state in the economy.
Komorowski would be expected to smooth the way for the government to continue privatizing state-run firms and trim welfare benefits; Kaczynski would probably block such moves.