According to preliminary results, Tusk's centre-right Civic Platform (PO) won nearly 40% of votes in the election, owing him a clear lead over his main rival, Jarosław Kaczyński and the Law and Justice party (PiS), which obtained just over 30%.
Projections based on preliminary results showed that PO and its preferred coalition partner, the Peasants' Party (PSL), could have enough seats to win a majority in the Polish lower house of Parliament – the Sejm.
The leader of the rural-based PSL, Waldemar Pawlak, who scored 8.2%, signaled he was ready to forge a new coalition with Tusk. Pawlak has been serving in the outgoing government as Deputy Prime Minister and Minister of the Economy.
The PAP state news agency quoted a senior PO politician as saying Tusk and Pawlak might yet fall short of a majority in Parliament and that PO might also try to take the Democratic Left Alliance (SLD) into a new coalition. The social-democrat SLD won a surprisingly poor 7.7%, according to the exit poll.
Analysts say the main surprise was the surge of a new party, the Palikot's Movement (Ruch Palikota), which has been campaigning against the dogma of the Catholic Church. Its founder Janusz Palikot, a wealthy businessman, has backed causes such as gay rights and the legalisation of soft drugs, striking a chord among young voters. Palikot's Movement, who was registerd as a party only on 1 June, scored 10.1% at the election and will be represented in Parliament.
The election turnout has hit a record low of 47%, some 20% less than in the 2007 elections.
Anna Pacześniak, political scientist at the Polish institute for International Relations at Wrocław University told EurActiv that she didn't believe the PO would seek a coalition with the social democrats. She called the SLD defeat a "catastrophe" and stressed that many leftist voters had turned to Palikot.
She said that Palikot did not want to enter in to a coalition with PO, but its leader has indicated that if the PO-led coalition would need help in Parliament, Palikot would give its support.
According to Pacześniak, the defeat of PiS was less dramatic, as the party had lost only 1% in comparison to the 2007 elections. She said that the eurosceptic PiS had achieved its main goal by showing Polish society that a third of its citizens want a "different" future for Poland.
Polish President Bronisław Komorowski, a former Civic Platform lawmaker, is now expected to ask Tusk to form a government but he must first wait for the official election results, expected on Tuesday evening.
"I hope that it will be possible to reduce the time necessary for creating the government ... to a minimum," Komorowski said on Sunday evening, quoted by Reuters.
According to Pacześniak, Tusk would probably keep most of the ministers of the outgoing government, which would also greatly help the running of the Polish EU Presidency.
"The election is good news for the Polish Presidency, it shows that everything will continue smoothly," Pacześniak said.
The election result is a personal triumph for Tusk, 54, a pragmatic liberal conservative from near Gdansk on Poland's Baltic coast. He is well known as an advocate of the community method in EU affairs and takes aim against what he calls "a new wave of euroscepticism" in the Union.
