According to the first official estimates published after midnight, Komorowski won 39.69% of the vote while 37.68% went to Jarosław Kaczyński, leader of the conservative Law and Justice (PiS) party.
Jarosław is the twin brother of late President Lech Kaczyński, who died in a plane crash in Russia on 10 April (EurActiv 10/04/10).
The turnout was 53.57%, slightly higher than in the last presidential election in 2005.
About 30 million Poles out of a population of 38 million were eligible to vote.
Polish left is back
According to many commentators, the real winner, however, is Grzegorz Napieralski, the candidate of the Left Democratic Alliance (SLD).
Although he came in third place with around 14%, Napieralski secured many more votes than he had been expected to two months ago, when the campaign started. His performance gave the Polish left hope of returning to the front of the Polish political scene, analysts said.
"The left is back," declared Aleksander Kwaśniewski, former president and an ex-leader of the SLD.
Prime Minister Donald Tusk expressed satisfaction with the result obtained by Komorowski, and said he would look ahead to the second round with optimism. "Everybody knows what the choice between Komorowski or Kaczyński means for Poland," Tusk added.
Jarosław Kaczyński served briefly as prime minister from 2006 to 2007. During that time, his nationalist views, and in particular his deep suspicion of Germany and Russia, severely strained Poland's relations with its neighbours as well as with the European Union.
If elected, Kaczyński is likely to use his presidential veto to block some reforms, just as his brother did. However, he toned down his rhetoric during the campaign and said he would seek compromises if elected, hoping to win over centrist voters.
Commentators did not dismiss Kaczyński's chances of winning the run-off.
"We got one big loser, Komorowski," sociologist Jadwiga Staniszkis told Polish TV station TVP Info. "He paid a huge price to gain a small difference [of votes]. He paid that by turning to the left and washing away the liberal image," Staniszkis explained.
In her opinion, Jarosław Kaczyński and Grzegorz Napieralski both came out as winners and Komorowski was the one who should worry ahead of the run-off.
"It will be better for Poland if the president was the person who can cooperate well with the government," historian and former Foreign Minister Władysław Bartoszewski is quoted by Gazeta Wyborcza as saying.
If Komorowski wins the run-off, the Civic Platform will have no excuse not to deliver its promises, writes Piotr Gabryel, deputy editor-in-chief of conservative newspaper Rzeczpospolita, Many analysts believe the real campaign will begin now and predict that the outcome is likely to be very tight.
