In one of the more memorable lines of the 1984 election campaign, New York Gov. Mario M. Cuomo said from a pulpit at the University of Notre Dame, "God should not be made into a celestial party chairman."

That remark by Cuomo, one of the nation's most prominent Roman Catholic politicians, highlighted the extraordinary degree to which the Roman Catholic Church, until recently a relatively quiet voice in national affairs, has become a highly visible player on the political scene in the last two years.

From the March 1983 pastoral letter on nuclear war, which engaged church leaders in a contentious battle with the Reagan administration, to criticism of Democratic vice-presidential nominee Geraldine A. Ferraro's statements on abortion by the archbishop of New York and other prelates, to the pastoral letter on U.S. economic policy released yesterday, the church is weighing into U.S. public policy debates as never before. The new activism among the church's 290 American bishops comes as the nation's 52 million Catholics, who form its largest religious voting bloc, appear to be reexamining their traditional allegiance to the Democratic Party. President Reagan last Tuesday captured 56 percent of Catholic voters, according to exit polls, compared with the 47 percent he received in 1980.

"The pastoral on war and peace marked the significant emergence of an era of involvement of the bishops in matters of public policy," New York Archbishop John J. O'Connor said in an interview. "Since colonial days, the bishops had taken a very low profile because they felt they had to prove that Catholics were loyal, patriotic citizens and criticism of government activities could jeopardize that status."

The activism of bishops who have come to power in the last few years reflects the spirit of the extraordinary revolution within the church wrought two decades ago by the liberalizing Second Vatican Council. Nonetheless, their newly aggressive stance has sparked debate within the American church over how much political influence bishops should try to exercise and what issues they should emphasize.

"We are probably maturing more and more as a church," O'Connor said. "In the U.S. over the past two centuries, Catholics have felt like they were second-class citizens. Now we come more and more to recognize not only our rightful role as citizens but our responsibility as church leaders to contribute to the body politic."

Rep. Henry J. Hyde (R-Ill.), the Roman Catholic leader of antiabortion forces in Congress, said wryly, "The bishops have been swept away by the prophet motive -- that's P-R-O-P-H-E-T." With the pastoral on the nuclear arms race calling for curbs on development of nuclear weapons, "The bishops became good copy because they were saying things that met with the approval of the major media," he said. "The bishops were arrayed against the administration, and that made for good theater."

The bishops' high profile has produced a backlash from left and right, however. Last week a group of conservative Catholic businessmen, including former treasury secretary William E. Simon and former secretary of state Alexander M. Haig Jr., moved to intercept the new economic pastoral, a liberal document that offers little comfort to the Reagan administration, with an alternative celebrating the virtues of capitalism.

Cuomo clashed publicly with O'Connor during the summer after the archbishop declared, "I don't see how a Catholic in good conscience can vote for a candidate who explicitly supports abortion." The New York governor, who opposes abortion but upholds the 1973 Supreme Court decision allowing it, took the comment personally.

"You have the archbishop of New York saying that no Catholic can vote for New York Mayor Ed Koch, no Catholic can vote for City Controller Jay Goldin, for New York City Council President Carol Bellamy, nor for New York Sen.Pat Moynihan or Mario Cuomo," he fumed.

O'Connor backtracked, contending that he had been "misinterpreted" and was not telling anyone how to vote. In a televised news conference in September, however, he took issue with Ferraro by name, saying she had mistakenly "given the world to understand that Catholic teaching is divided on the subject of abortion." That, coupled with the declaration of Boston Archbishop Bernard Law and 18 New England bishops that abortion was the "key issue" in American politics, led to fears that the church hierarchy indirectly was endorsing the candidacy of Reagan, who favors restrictive antiabortion laws.

"It is not wise for prelates and politicians to be tied too closely together," Cuomo warned in his Notre Dame speech. Defending his position on abortion, he added, "We know that the price of seeking to force our beliefs on others is that they might someday force theirs on us."

The impression of partisanship was strengthened when Philadelphia's Cardinal John Krol appeared at a rally with Reagan, praising his support for tuition tax credits.

The incidents -- and the extensive publicity they received -- have caused an uproar in the church. Bishop James W. Malone, head of the National Conference of Catholic Bishops, issued a statement three weeks before Election Day, declaring, "We do not seek the formation of a voting bloc . . . . The content of Catholic teaching leads us to take positions on many public issues; we are not a one-issue church."

Malone said the bishops "give special emphasis to two issues today. They are the prevention of nuclear war and the protection of unborn human life."

Concerned that the statements by O'Connor and Law had "confused" Catholics into thinking they should vote on the basis of a politician's stance on abortion alone, 23 bishops, led by Auxiliary Bishop Thomas J. Gumbleton of Detroit, issued a statement declaring themselves "gravely concerned" that abortion was eclipsing "the threat of nuclear warfare" in the campaign.

In a major speech at Georgetown University a few weeks ago, Cardinal Joseph Bernardin of Chicago, one of the nation's most influential church leaders, emphasized that the church's approach must be one of "a consistent ethic of life," the support of a "seamless garment" of issues that "consciously connects" the issues of war and abortion.

He acknowledged, however, "We obviously do not have a consensus on this point at present -- even within the church."

Bernardin also made clear that the "seamless garment" includes the moral teachings in the new economic pastoral, a document reflecting the "fairness" theme emphasized this year by presidential nominee Walter F. Mondale and other Democrats.

Conservatives on the whole take a dim view of the "seamless garment."

"The seamless garment seems to protect a lot of liberals who get two out of three: they're for the liberal welfare agenda, they're against our defense policies, but they never vote with us on abortion," said Hyde, a member of the House Foreign Affairs Committee, who objected to the bishops' pastoral on nuclear arms.

O'Connor, although a former military chaplain who was the most hawkish of the five bishops who drafted the pastoral letter on nuclear arms, appears to embrace the "seamless garment" argument, with a subtle difference in emphasis. "Those who would try to derive comfort from the 'consistent ethic of life' approach, by interpreting it to suggest that an officeholder's or a candidate's position on abortion does not matter so long as positions on other life issues are acceptable, miss the point of Cardinal Bernardin's argument altogether," O'Connor said in a speech last month.

O'Connor, a registered independent who said he votes "for the man," bristles at the suggestion that he might have come across as a Republican partisan. "I have said many things that could be considered harmful to the Reagan administration," he said.

In a speech in Chicago last week, O'Connor praised the letter on the economy and, in language hardly designed to reassure advocates of an unbridled free market, called for "a reappraisal of economic approaches that virtually institutionalize starvation and attendant evils for millions and millions of people all over the world . . . ."

Former representative Robert F. Drinan (D-Mass.), a priest who served in Congress until forced by the Vatican to resign, said, "There is no fundamental cleavage among the bishops . . . there are not two polarizing schools. There are different emphases." Drinan, who voted in Congress to fund Medicaid abortions, campaigned for another pro-choice candidate this fall, Rep. Tom Harkin (D-Iowa). Harkin's election to the Senate, and that of another pro-choice Democrat, John F. Kerry in Massachusetts, indicates that although Reagan carried both states with a heavy Catholic vote, Catholics are not heeding calls to base their votes on the issue of abortion, Drinan said.

Though some critics believe that O'Connor crossed the line of partisanship by taking on Ferraro, there is support in both parties for the bishops' activism on various issues. There is precedent, politicians note, in the longtime activism of black churches in the Democratic Party and in the recent courtship of fundamentalist Christians by the GOP.

Nonetheless, many Catholics would prefer to see the church stay out of controversial public policy debates.

"The bishops have gotten themselves into a box," said J. Brian Benestad, a theology professor at the University of Scranton who has written a book on the involvement of bishops in social issues. "They have a genuine desire to promote justice, but they think they've got to be like congressional aides and solve political problems . . . . The church has a duty to outline principles and educate people. Then people can make up their own minds."