The Civic Platform, which is Poland’s biggest opposition grouping, has been holding a primary election within its own ranks to select a contender.
Many commentators have said that the favourite within the party is deputy parliamentary Speaker Małgorzata Kidawa-Błońska, who has presented herself as a moderate, conciliatory figure able to reach out to voters from across Poland’s bitterly divided political landscape.
Kidawa-Błońska is being challenged for the nomination by the mayor of the western city of Poznań, Jacek Jaśkowiak.
The Civic Platform is expected to select its candidate at a national convention in Warsaw on Saturday attended by some 700 delegates, including deputies, senators, members of the European Parliament and local activists.
Meanwhile, Poland’s ruling conservatives last month reaffirmed their support for incumbent President Andrzej Duda, who is expected to seek re-election in May.
Ex-European Council President Donald Tusk, a former Polish prime minister, has previously declared he would not run for president next year.