Tusk's Civic Platform is ahead of the Law and Justice Party headed by former Prime Minister Jaroslaw Kaczynski by 10 percentage points, The New York Times reports. If Tusk and his party win Sunday's election, he would be the first prime minister to serve two consecutive terms since the fall of the Communist government.
Tusk, who ousted Kaczynski in 2007, has fostered ties with Germany and the rest of the European Union. Kaczynski was more pro-American.
In his book, "Poland of Our Dreams," Kaczynski charged the Stasi, the once-dreaded East German secret police, helped German Chancellor Angela Merkel's political rise.
Pawel Swieboda, president of demosEuropa, said Tusk has been running a kind of campaign new to Poland, traveling the country in a campaign bus.
"It's a kind of listening campaign, and so far, it seems to be working," Swieboda said.