I followed Lech Walesa to the Lenin steel mill at Nowa Huta near Krakow last month and watched him try to cajole the 40,000 workers at Poland's largest steel works not to strike. On that day, facing an auditorium packed shoulder to shoulder with several thousand workers, many wearing red and white Solidarity baseball caps, Walesa succeeded. But today Poland is in the clamp of martial law. Walesa is apparently in custody, and the workers at Nowa Huta are reported to have gone on strike, notwithstanding the threats of death penalties.

From up close, Walesa struck me as magnetic. He drilled his audience with a rapid-burst single-pitch delivery: "We cannot keep frightening people. There are so many issues and problems, but we cannot strike over all of them. I think we must change our approach. We must show the real strength of our union by improving conditions . . . . We keep behaving like that farmer who got 10 hectares of land. He did not cultivate it and already he wanted 10 more."

At Nowa Huta, Walesa was going over the heads of his more radical colleagues on the National Commission of Solidarity. "Society must understand that compromise is not treason," he said. In the 50 minutes of questions and answers, the strike fever cooled. Near the end one man rose: "I do not have a question but a comment. Mr. Lech, it does not mean anything that at the (Solidarity) Congress you got 55 percent of the vote. Here at the grass-roots level you have behind you 99.9 percent of us." The applause lasted a full minute. The workers went back to work, and Walesa drove off to a dilapidated house 15 miles away to assure himself that a small girl to whom he had promised a hearing aid had actually gotten it.

Four and a half weeks later on Dec. 13, Poles woke up to martial law, hours after Solidarity leaders meeting in Gdansk, choosing a more radical tack, proposed a nationwide referendum on setting up a non-communist government.

It is easy to say that Solidarity's radicals, who put forward that proposition in an outpouring of frustration and revolutionary naivet,e, provoked the crackdown. The truth is that the militant wing of Solidarity allowed itself to be entrapped by the hard-line elements of the Communist party, which dreaded the gradual redistribution of power that Walesa represented.

Stefan Olszowski and other hard-line Politburo members have systematically sabotaged the hopes held out by the government in its historic pact with Solidarity in August 1980. Promised economic reforms have been delayed. The rule of law is as remote as ever. Those who beat up Solidarity members in the Bydgoszcz police raid last March were never punished. Solidarity was never given full access to television.

For the last 15 months, Poland's rulers have given with one hand and taken away with the other. "Solidarity is accused of slowing down economic recovery with strikes," one Solidarity intellectual told me. "But in fact it is the authorities who are on strike. They have not delivered what they promised."

Olszowski, who manages the official mass media, has waged a ceaseless campaign blaming Solidarity for the nation's economic problems, pronouncing the union's tactics intransigent and depicting Walesa as a troublemaker. Particularly in recent weeks, the Solidarity militants unwittingly steered the union toward the trap the authorities were waiting to close. On Dec. 3, Walesa said: "Confrontation is inevitable and it will take place. I wanted to get to this confrontation in a natural way when virtually all the societal groups would be with us. However, I have miscalculated . . . it turns out that we will not move along this road any further. So, we are picking a road for a lightning- speed maneuver . . . we are aware that we are dismantling this system."

It remains to be seen whether the imposition of martial law will arrest the "dismantling" Walesa spoke about. In a curious way, he remains the center of attention, the magnetic politician whose persuasive powers are critical to the outcome. Although isolated, he has managed to smuggle out messages urging Poles to help each other, to avoid bloodshed and to engage in non-violent strikes in large factories where sit-downs can have the most effect.

Gen. Wojciech Jaruzelski has imposed martial law, but he has not shown that he can force Solidarity's 10 million members to go back to work. For that he still apparently needs Lech Walesa.