Paris.--THE POLLS still say that Lech Walesa will win Poland's run-off presidential election today, but it is no sure thing. Given the frightening turn Poland's affairs have taken, it is essential that he do so. It also proves to have been essential that he and not Tadeusz Mazowiecki won the first round November 25.
One's deepest sympathy was with Mr. Mazowiecki, a self-effacing intellectual attempting to carry out a rational reconstruction of Poland's ruined economy. He has been doing what the International Monetary Fund and Harvard University's Jeremy Sachs have advised. The result, in the short term, has been a hundredfold multiplication of unemployment, a fall by a third in real incomes, a fall in industrial output, and a rise in inflation to nearly 1,000 percent on the year. Out of this shock treatment a purged economy is supposed to emerge.
Whether it will work is hotly debated. Whatever the merits of the policy, neither it nor anything like it could be carried out against the opposition of Lech Walesa. Mr. Walesa proved incapable of retiring to the history books, where his place would have been golden, as inspired leader of Solidarity and of Poland's liberation from communism. He has to get back into public life. He may in the end be sorry that he has done so. That makes no difference now. So long as he is in public life, no one can run Poland's affairs with Mr. Walesa against him. Thus it is better to make him president, where he has to take responsibility for what the government does.
His argument has been that he will make little basic change in what the Mazowiecki government has been doing. He may not even make much change in the personnel of government, he says. He simply thinks that with the changes, and with him in charge, traveling the country to preach and exhort and cheer reform along, things will go better.
He probably is right, but that depends on whether he is elected today. His campaign has unleashed in Poland a spectacular conflagration and conflation of popular illusions, distortions, misunderstandings, dreams and fears. The national political consciousness has been revealed as in a state close to hysteria.
The rival candidacy of Stanislaw Tyminski has revealed the degree to which the nation has been unhinged by four decades of communism and lies, and the half-decade before that when the Nazis attempted to enslave or exterminate the Poles, and the bleak years of authoritarianism before that, which followed the ephemeral glory of national reconstitution in 1918 after a century and a quarter of partition and disappearance from the map. No nation in Europe has undergone the ordeals Poland has undergone. Today, like Job, the Poles might ask: ''Must I have nothing left to daunt me? Must each calamity be felt as soon as feared?''
This man, Stanislaw Tyminski, who has come from an ambiguous exile in Peru and Canada to defeat Tadeusz Mazowiecki in the first round of the election, tells the Poles that if they vote for him against Lech Walesa they will be individually rich and Poland will be earning billions within weeks.
He talks with the menacing para-rationality of the cult indoctrinator. He says he possesses a ''fourth dimension'' of human understanding. Asked difficult questions by journalists he often simply gives a thin smile and is silent. Or he will reply, ''That is an interesting question'' and add nothing. He says that Solidarity and the government conspire against him and against the ordinary Pole, and will sell the country to foreigners.
He threatens undisclosed -- as yet undisclosable -- revelations about his enemies. He says that if he is elected Lech Walesa will have to flee the country. He says Poland must have the nuclear bomb, which he calls the ''Jew-bomb.'' He seems quite mad. The situation is ridiculous and at the same time terrifying. Must Poland endure this too?
Adam Michnik, once Lech Walesa's close friend and adviser, in the days when Solidarity was freeing Poland, spoke bitterly to his former friend last week, at a meeting where the members of the Solidarity Parliamentary Group tried to save something from the wreckage of the first round of the election.
Mr. Michnik told Mr. Walesa: You did this, '' . . . you are responsible for this caricature of a politician. You, with the brutal message you tried to transmit. You demanded that political men say what religion they were. I am a Jew. I took that like a slap in the face. I will remember it.'' Mr. Walesa could only reply, ''Adam, I am sure that we will find one another on the way, for Poland's sake.''
They have to do so. Any other way lies a national delirium of unfulfillable promises and expectations, followed by anarchy, or worse. Now we see the depth of the trauma inflicted upon society by what the Nazis and the Bolsheviks did to the Poles -- and to the rest of Eastern Europe. If those still sane do not stand together, the regime of madmen will resume.