Shortly after his surprise election last month as leader of the Polish Communist Party, Stanislaw Kania said he had one overriding mission. It was to ensure that Poland would never again experience a repetition of the social, economic and moral crisis that brought it to what he described as "the verge of national catastrophe."

Five weeks later, the theme of "it must never happen again" still recurs in the new leader's speeches around the country. But, as problems pile up and the economy slides deeper into debt, a more immediate preoccupation appears to be troubling him. It is simply this: how to extricate Poland from its present crisis.

There are arguably few polticians in power today who face such a plethora of troubles as the 53-year-old Kania. He has to deal with a divided party bureaucracy anxious to retain its power and privileges, assertive opposition from the Roman Catholic Church and newly independent trade unions, and a Soviet leadership suspicious of any dramatic change of course.

To complicate his balancing act still further, he is attempting to win the trust of a thoroughly skeptical population at a time when there is little to buy in the shops -- despite big pay raises granted over the last few months.

In short, Kania's room for maneuver is limited. His position is certainly more precarious than that of either of his disgraced predecessors, Edward Gierek and Wladyslaw Gomulka, when they came to power in 1970 and 1956 respectively. Both men started off with a good deal of public confidence and an economy in much better shape than it is now.

Addressing a stormy session of the party's Central Committee a week ago, Kania reminded Poles that the crisis is not yet over and Poland faces enormous economic problems and numerous threats to its stability.

Kania's words reflected the uncertainty felt by many of his countrymen about the final outcome to what he called "the gravest crisis" since World War Ii. Given many surprising turns over the last two months, it is futile to predict how it will all end.

Possible scenarios range from a genuine movement toward some form of pluralistic communism to a Stalinist backlash supported by Soviet tanks.

Much will depend on the skill displayed by Kania, a former village blacksmith who rose quietly through all levels of the communist apparatus. While totally lacking charisma, he does have other qualities -- such as simplicity, organizational ability and a sense of fairness -- which could be valuable assets if he is given a chance to display them.

In December 1970, after workers' riots had toppled Gomulka's tired authoritarian regime, Gierek swiftly set the tone for a new style of government. People responded to his call, "Will you help me?"

Kania, by contrast, has remained a more shadowy figure. His appointment as Gierek's successor drew little reaction from ordinary Poles, either negative or positive. Even the joke-tellers seem to have had difficulty summing him up.

One of the few jokes told about him so far plays on his name (kania in Polish is a large and tasty type of mushroom), his anonymous background and his sudden rise to power during the night between Sept. 5 and 6. Soon afterwards, Poles were saying: "Kania just sprang up overnight."

In fact, Kania's origins are not as obscure as all that. For the last 10 years, he was an influential member of the Polish leadership. His responsibilities included security, the Army, and relations with the Catholic Church.

As security chief, Kania won a reputation for moderation and good sense. He also won some firm friends as a result of his interventions with the police on behalf of people who were unjustly harassed or under suspicion. A writer, whom Kania helped, spoke highly of his sense of justice.

A senior church official recalled that Kania took a tough line during negotiations prior to the pope's visit to Poland in 1979. But he added: "He was, after all, the policeman." Other sources said Kania had helped improve church-state relations by insisting that the pope should be allowed to return to his homeland, albeit on strict conditions.

A small, chunky man, Kania lives in a Warsaw apartment and is on friendly terms with his neighbors -- who say they even used to see him out shopping, a rare pastime for a high official. According to his biography, he fought in the resistance during the war and joined the communists in 1945 in his home village of Wrocanka in southeastern Poland. In the early 1950s, he moved to Warsaw and made his career in the party apparatus. He was elected a candidate member of the Politburo in 1971 and a full member in 1975.

An uninspiring speaker, his words carry more conviction in informal sessions, when he speaks simply and directly.

Unlike Gierek, who pitched his appeal directly to the people, Kania has concentrated his efforts on restoring party morale and his audiences have been made up mainly of party activists. He has urged them to expel corrupt members from the ranks and rebuild their ties with the workers.

Given Kania's own temperament and the Polish people's disillusionment with all politicians, this was probably the only sensible way to proceed. But it has its dangers. The most obvious is that, instead of leading the country out of the crisis, Kania could become a prisoner of a party apparatus deeply resistant to change.

Before the Central Committee plenum, there were well-sourced leaks that he had been persuaded to make a decisive break with the past and quickly convene an emergency congress to draft a new party program. If the party failed to set a lead, it was argued, thecountry would drift into a new and even more serious crisis -- and Kania would go the way of his predecessors.

Kania did come out in favor of reforms. But his approach was cautious and did not go nearly as far as the reformists had hoped. He also failed to suggest any specific date for the congress because Central Committee members were not prepared to vote for their own dismissal.

The inevitable result was compromise. Kania had managed to nudge the party one step further towards reforming itself. Several Gierek aides had been made scapegoats for past "mistakes" but no decisive strategy was mapped out.

One of the politicians Kania needs to get on his side if he is to push his ideas is the controversial former security chief, Gen. Mieczyslaw Moczar. Now 67, Moczar led an anti-Zionist campaign during the 1960s and helped suppress student unrest. He was the leading candidate to succeed Gomulka but his nationalist views made him suspect to Moscow. In 1971, it was Kania who took over the security portfolio when Moczar was eased out of the Politburo by Gierek.

After nine years in the political wilderness, Moczar is once again a force to be reckoned with. The issue on which he has made his return is corruption. In what appeared to be largely a sinecure as chairman of the Supreme Control Commission, he quietly accumulated evidence of misdeeds in high places. Under Gierek, there was not much he could do with the information -- but suddenly it has become valuable ammunition for use against his former enemies.

The rise in Moczar's important illustrates that the current power struggle here is not simply a battle between discredited hard-liners and resurgent reformists. It is a complicated realignment and settling of accounts involving many different factions and regional interest groups.

Working largely behind the scenes, Kania has tried to shape a new coalition within the party. For the moment, he has retained the trust of the Kremlin. But, with the party still in disarray, the pace of Polish politics has been set by Solidarity, the new independent union led by Lech Walesa, which has maintained an unremitting pressure on the authorities.

Kania's supporters praise his unassuming approach, his deliberate refusal to indulge in dramatic gestures, and the determination with which he as attempted to rally what one party memberdescribed as "a defeated army." But many influential Poles are concerned about weaknesses at the top.

An economist at Warsaw University remarked: "In this part of the world, we need a strong leader, someone whom both the Russians and the people can respect. The absence of such a man at present worries me."