Free market advocate Donald Tusk has a slender lead in Poland's presidential election with almost all votes counted, but a second round will be necessary.
Kaczynski supporters were pleased at his showing
Latest figures give Mr Tusk 35.8%, with the other centre-right contender Lech Kaczynski on 33.3%.
But with neither candidate near the required 50% majority needed for outright victory, a second round will be held in two weeks' time.
Ten other candidates are all trailing well behind the two front-runners.
The turnout was just under 50%, prompting former President Lech Walesa to complain that Poles were wasting the reforms he battled for in the 1980s as the leader of the Solidarity trade union.
"When I fought for democracy, I thought my compatriots would use it, but now I wonder - what was all this suffering for, these searches, beatings, arrests?" he said.
Mr Tusk, 48, said that he was "proud of the result and proud of Poland", while Mr Kaczynski, 56, for his part was "certain that in the long run we will win".
RESULTS SO FAR
Donald Tusk - 35.8%
Lech Kaczynski - 33.8%
Andrzej Lepper - 15.6%
Turnout - 49.6%
Second round on 23 October
Both men must try to win the support of voters who backed the candidates who will be eliminated from the second round. Analysts say the votes of the third-placed candidate, populist Andrzej Lepper who polled 15.6%, may well benefit Mr Kaczynski.
Mr Kaczynski is also likely to attract conservative Catholics and nationalists, while Mr Tusk's strong pro-EU stance makes him more attractive to moderates and liberals.
Tusk: "Proud of Poland"
Mr Tusk's Civic Platform and Mr Kaczynski's Law and Justice Party were also neck-and-neck in parliamentary elections held a fortnight ago.
The two parties have started negotiations on forming a coalition in parliament.
As Law and Justice won 155 seats to Civic Platform's 133, it has nominated the new prime minister, the relatively little-known Kazimierz Marcinkiewicz.
Critics say that he was chosen in preference to Lech Kaczynski's identical twin brother Jaroslaw, in order not to dent Mr Kaczynski's hopes for the presidency.
Both men favour free market economics, but Mr Kaczynski puts more stress on Catholic and family values.
Mr Tusk has spoken of the "great opportunity" offered by Poland's entry to the European Union last year.
Kaczynski thinks he is well-placed for the run-off
But Mr Kaczynski focused his attacks on the outgoing government of ex-communists, accusing it of corruption and calling for "moral change".
If elected, he wants Poland to become a new republic, the fourth in its history.
The current president, former communist Aleksander Kwasniewski, is unable to stand again, having served the maximum two five-year terms permitted.
Under Poland's constitution, the president has less power than the country's prime minister, but retains a significant say in foreign policy.
Mr Tusk has said that, if elected, he would seek to make more effective use of the president's powers.