Not since the waning days of Pope Pius XII's pontificate in 1958, according to Catholic University historian Robert Trisco, have there been so few princes of the church in this country.

The retirement last month of

Roman Catholic Cardinal John Krol of Philadelphia left Roman Catho- lics in this country with three ac- tive cardinals, the fewest in 30 years.

Only Cardinals Joseph L. Bernardin, 59, of Chicago; Bernard F. Law, 56, of Boston, and John J. O'Connor, 67, of New York continue to serve the church in this country. American Cardinal William

W. Baum, 61, heads the Vatican's Congregation for Education in Rome.

Cardinals' chief duty is to gather on the death of a pope and choose one of their number as his successor. But appointment to the office of cardinal, the second-highest post

in the church, carries prestige

and access to the centers of

power.

The shortage of American cardinals at home is a turnaround since 1969, when an all-time high of nine cardinals headed dioceses here and a 10th American, Cardinal John Wright of Pittsburgh, was assigned to a high Vatican post.

Worldwide, there are 136 cardinals, down from a high of 152 in 1985. Only 98 are younger than 80, the age limit for eligibility to vote in the election of a pope.

Having fewer than 100 cardinals eligible to elect a pope "is really unusual," said a knowledgeable observer who asked not to be identified.

The shrinking numbers have fueled rumors that Pope John Paul II will soon name several new cardinals to bring the total closer to the upper limit of 120 potential electors, set by Pope Paul VI in 1973. Washington Archbishop James A. Hickey is considered to be among the leading contenders.

Few rules govern the pope's selection of a cardinal, but one of the best predictors is locale. Cardinals are most likely to be appointed in major dioceses where there have been cardinals in the past.

By this criterion, pundits agree, leading American contenders include Hickey, 67; Archbishop Roger Mahoney, 51, of Los Angeles, and Archbishop John May, 65, of St. Louis. May is president of the National Conference of Catholic Bishops.

The multiracial, multiethnic diocese of Los Angeles is the most populous and one of the most important jurisdictions of the church in this country. But Mahoney's

elevation may be delayed, be- cause his predecessor, retired

Cardinal Timothy Manning, 77, is alive.

That does not necessarily rule out naming the incumbent. Popes usually do not explain their choices, but in some instances, such a circumstance appears to have been a factor in skipping over the incumbent.

May's predecessor, retired Cardinal John J. Carbury, also is living but at 83 is no longer eligible to vote at a papal conclave.

The death last summer of Cardinal Patrick O'Boyle of Washington could clear the way for Hickey to receive the cardinal's red hat. And some observers believe that Hickey has earned ecclesiastical points with his strict, by-the-book dealings with the dissent of the Rev. Charles Curran and others at Catholic University and in the archdiocese in recent years.

Washington's geopolitical importance also could enter into the decision. "I've told the nuncio {the pope's representative in this country} that the capital of the free world should have a cardinal," said Msgr. John Tracy Ellis, dean of Catholic historians, who believes Washington should take precedence over dioceses that historically have had cardinals. "To persons in other parts of the world, what does Boston mean?" he asked.

Retired cardinals are still living in Detroit and Philadelphia. And in Baltimore, the other archdiocese with a tradition of cardinals, Archbishop William Borders, 74, is considered too liberal to be named by the present pope.

There is considerable speculation that Pope John Paul II could recognize the rapid expansion of Catholicism in the South and Southwest by naming a cardinal there. Among the names mentioned most often is San Antonio Archbishop Patrick F. Flores, 58.

Naming a Hispanic cardinal would be in harmony with John Paul II's move to increase the number of Third World churchmen in the College of Cardinals.

The Rev. Celestino Migliore, first secretary of the Apostolic Nunciatore here, said that about 70 of the church's cardinals come from Africa, Asia and South America.

Thirteen of the 28 cardinals in the most recent class of cardinals, named nearly three years ago, were from Third World countries, including Ethiopia, Nigeria and India.