Polish Leaders Close Ranks to Fight Challenger : Election: Walesa and former foes move to reunify Solidarity, fend off upstart Tyminski.

The Polish political leadership began binding up its wounds Tuesday, making the first efforts to try to unify the old Solidarity coalition behind Lech Walesa to defeat the upstart stranger from Canada who knocked the prime minister out of the presidential running in Sunday’s election.

Tadeusz Mazowiecki, the prime minister who finished third in the balloting, agreed to stay on in charge of a caretaker government until after the Dec. 9 runoff election, which will pit Walesa against Canadian businessman Stanislaw Tyminski. Mazowiecki’s government resigned Monday in the wake of his defeat.

The liberal wing of the Solidarity camp, which had backed Mazowiecki, was trying painfully to shake off its initial anguish over the defeat, with some prominent figures urging Mazowiecki’s supporters to throw their votes to Walesa in the runoff against Tyminski. And Solidarity Chairman Walesa himself began building bridges back to Mazowiecki supporters.

The overriding priority was clearly to head off Tyminski, viewed by both camps as an interloper and opportunist, a 42-year-old emigre who spent the last 20 years making money in Canada and Peru while the Solidarity stalwarts remained in Poland, battling the Communists.

Adam Michnik, editor of Gazeta, Poland’s largest-circulation newspaper, and an old Walesa ally who had vociferously opposed the Solidarity union leader in the first round of voting, wrote Tuesday that “Walesa is the only candidate who can be considered.

“Walesa’s victory will bring a great risk for Poland,” he continued. “Tyminski’s victory must bring, as an absolute certainty, the degradation of our country.”

For his part, Walesa said in a news conference in Gdansk that he intends to phone Mazowiecki in an attempt to smooth the waters and to unify Solidarity supporters against what he said he had earlier warned of--a “third force” in Polish politics.

“Those people who were with Mazowiecki, who really worked so hard, did not want to understand,” he said. “This cold shower will wake us all up, and we will think seriously about reforms in Poland. A third force is possible and capable of overthrowing us all.”

Meanwhile, the Polish press cut loose on Tyminski on Tuesday with a barrage of hostile questions concerning his background, his businesses, his past travels to Poland, his stand on the 1981 martial law declaration.

“Could you please explain,” an initial questioner asked, “accusations that you are an agent of the KGB, that you are sick with epilepsy, that you are involved in the drug trade in South America and that each time you traveled to Poland in the 1980s, you traveled through Tripoli, Libya, where you picked up your visas?”

“A lie, a lie and a lie,” Tyminski answered.

Tyminski brought audible gasps of disbelief from the Polish reporters when he declined to condemn the 1981 imposition of martial law by Gen. Wojciech Jaruzelski, now the lame-duck president.

“I hope,” he said, “that this country now understands how much has been done for it by President Wojciech Jaruzelski, because at that moment (in 1981) the country was in unusual danger from within . . . because the Poland that did the injury was for so many years our own.”