Pope John Paul II's apparent support for a local anti-abortion campaign has deeply disillusioned left-of-center Itallans who had been pleased by his election to the papacy and has contributed to a growing conviction that the new, Polish-born pontiff is a staunch conservative, and a rigid one at that.

After three months at the helm of Roman Catholicism, the 58-year-old pontiff's scores of speeches indicate a belief in strict orthodoxy, both in terms of doctrine and discipline.

His style -- characterized by an unusual number of trips out of the Vatican and by a high degree of visibility and careful use of his charisman -- is new. But the substance of his papacy so far appears to be highly traditional.

Furthermore, the new pope's unequivocal statements supporting religous freedom and opposing Marxism, suggest that in contacts with Eastern Europe, and with Communist governments in general, he is likely to be much more of a militant than the conciliator that some had imagined.

But Pope John Paul's initial period of good relations with the Catholic and non/Catholic left here came to a definitive end with his recent out-spokenness on abortion, a delicate political issue here where a recent liberal law is encountering difficulties.

Since his public praise of the hundreds of Italian doctors who have taken advantage of a claus in that law to refuse to perform abortions, several Italiam observers have suggested that the former archbishop of Krakow, Poland, ought to have called himself Pope Pius XIII.

Pope Pius XII, who died in 1958, was known for his interference in Italian affairs. The persent pope's nameskes, John XXIII- AND Paul VI had a reputation for being more flexible and subtle.

The sharpest criticism of the pope's outspokenness against abortion has come from Italian liberals, who had warmly welcomed the mid-October election of Polish Cardinal Karol Wojtyla to the papal throne.

They reasoned that as a foreigner unfamiliar with Italian politics and not linked to the ruling Christian Democrats, the first foreign pope in 455 years would be likely to keep aloof from Italiam political affairs.

They were not surprised by the pope's condemnation of abortion, a moral issue on which the church has always been adamant. But his apparent support for an anti-abortion campaign launched by top Italian prelates led to charges from the left of intervention and to an anticlerical resurgence.

Last week many feminists were outraged when the pope praised motherhood, telling girls in an audience of 15,000 school children that "maternity is a woman's enternal vocation."

And since acceding to his thrond, John Paul has also reaffirmed the doctrine of priestly celibacy, rejected the idea of women priests, emphasized worship of the Virgin Mary, turned down Anglican calls for intercommunion, praised the use of Latin, and asked priests to wear cleical garb and to stay out of politics.

Many of these positions conflict with trends in Latin America and are likely to come to the fore when the pope travels to Puebla, Mexico, later this month for the conference of Latin American bishops.

Conservative prelates there will be seeking revision of a recently adopted regional church policy statement calling on the Roman Catholic Church to back the poor and the oppressed against the area's many dictatorial governments.

There has also been initial disappointment among those who were looking to the new pontiff for greater emphasis on "collegial" power sharing with the world's bishops. At a recent audience with Canadian bishops, the pope rejected their request for relaxation of a church ruling that children may not receive their first communion until they have formally confessed their sins.

The pope's comments on abortion, condemning it as contraty to human dignity and unfair to unborn babies, came shortly after the archbishop of Florence, Cardinal Giovanni Benelli, referred to the new law as a "boil to be eradicated." Benelli called on Italian Catholics to use all the constitutional means at their disposal to eliminate it.

Benelli's words were widely interpreted as an encouragement to Italy's budding "Right-to-life" movement to launch a campaign for a national referendum on the subject. Others believe Benelli and his supporters want to use the abortion issue to disurpt the current truce between the Christian Democrats and the powerful Communists.

The most immediate result, however, was to convince the pro-civil rights and anticlerical Radical Party to begin its own drive for an abortion referendum that would further liberalize Italian law.

The recently passed Italian law permits free abortion on demand for all women over 18 in their first three months of pregnancy. When the law went into effect on June 6, 1978, Pope Paul VI is said to have turned down the idea of supporting a referendum.

Not only would a referendum. threaten to reactivate traditionally bitter political divisions between Catholics and non-Catholics here, but it could possibley interfere with delicate negotiations betwen Italy and the Vatican to renegotiate the 1929 concordat that governs church-state relations here.

The aging Pope Paul reportedly had also not forgotten the trauma undergone by the Italian church when church-backed opponents of divorce were overwhelmingly defeated in a 1974 national divorce referendum here.

Analysts have suggested that the new pontiff is developing an "interventionist" line on matters of conscience here that seeks to establish the church as the prime authority on moral and ethical matters.

Sen. Giovanni Spadolini, a Vatican historian calls this an attitude of "doctrinal restoration" that, if carried to the extreme, could contradict the conclusions of the 1962-1965 Vatican Council, at which a sharp distinction was made between religion and polictics.

Although he has so far made no major move on the crucial issue of the Vatican's relations with Eastern Europe, the new pope has shown no signs of renouncing his backround as a leader of the church as an opposition force in a Communist-ruled country and a fighter for religious freedom.

Since his election, Pope John Paul has made it clear he will continue his pressure on the atheistic government of Poland to allow the millions of Catholics there to worship fully and freely. Earlier this month, he told 200 Poles from his home town of Krakeow that he feels it his duty to attend ceremonies there in May marking the 900th anniversary of the death of St. Stanislaw, who was martyred by a Polish king.

Pope John Paul has repeatedly described the country's patron saint as "a spokesman of most essential human rights and the rights of the [Polish] nation." After a letter he wrote in these terms to his former diocese was censored by Polish authorities, the Pope initiated a weekly series f Polish-language masses beamed to Poland by Vatican Radio.

The first broadcast, delivered by the pope himself on Jan. 7, was conciliatory in tone. But only hours before, he had attacked Marxism for accusing religion of alienating man and said the Roman Catholic Church would not rest until all makind can worship in peace.

During the papacy of Pope Paul VI, the pope and his deputy secretary of state, Monsignor Agostino Casaroli, inaugurated a policy toward Communist-ruled states that used conciliation to better conditions for the church in Eastern Europe.

Casaroli's position at the Vatican has never been offically reconfirmed. There has been considerable speculation that he might be made a cardinal and promoted to secretary of state. But other sources believe that he may leave the Vatican altogether, which could mean that the conciliatory policies toward Eastern Europe might be revised.