If no contender wins over half the vote, under Polish election rules, a second round will be held two weeks later, on May 24.
Conservative Andrzej Duda, who has been president since 2015, is the favourite in the race.
Opposition contenders who have declared they will run for president include the centre-right Małgorzata Kidawa-Błońska of the Civic Coalition, Władysław Kosiniak-Kamysz, head of the rural-based Polish People’s Party (PSL); leftist Robert Biedroń; right-winger Krzysztof Bosak; and well-known journalist Szymon Hołownia.
Duda achieved a surprise win in Poland’s last presidential elections five years ago. He was a relatively unknown young challenger at the time but beat the centrist incumbent, Bronisław Komorowski, in the second round in 2015.
Poland’s Law and Justice (PiS) party won parliamentary elections later that year, a “double whammy” that saw the conservatives taking the posts of president and prime minister.
Since then, Duda has become one of the country’s most popular and recognisable politicians, criss-crossing Poland and conducting high-profile visits abroad, including to the United States, to which Poland looks as a guarantor of its security.
A survey carried out at the end January by pollster Kantar for private broadcaster TVN found that Duda was backed by 44 percent of voters.
His biggest rival, Kidawa-Błońska, was way behind on 24 percent, the poll found.
Though popular, Duda has drawn fierce criticism from the opposition, which has accused him of rubber-stamping decisions issued by the ruling Law and Justice party. Duda’s supporters rebut such criticism.
His spokesman said on Tuesday that Duda had signed into law controversial rules to discipline judges, a move that raised the stakes in a standoff between Poland and the European Commission, which has asked the EU’s highest court to freeze the new measures.
Critics have claimed that the disciplinary rules could undermine judicial independence and allow the government to gag dissenters.
But the governing Law and Justice party has insisted that sweeping changes are needed to reform an inefficient and sometimes corrupt judicial system tainted by the communist past.
Duda’s predecessors as president were former Solidarity leader Lech Wałęsa (1990–1995); Aleksander Kwaśniewski (who served in the post for two terms, from 1995 to 2005); Lech Kaczyński (who was killed in an air crash in 2010, the last year of his term); and Komorowski (2010–2015).