On March 8, President Reagan took to the presidential pulpit in Orlando, Fla., and in a speech before the National Association of Evangelicals described his domestic and foreign policies in almost entirely moralistic and religious terms.

Reagan accused his arms control and military spending critics of trying to place "the United States in a position of military and moral inferiority." He described the Cold War as a "struggle between right and wrong, good and evil."

And he said his administration's efforts to ban abortion, reinstate public school prayer and notify parents when teen-age girls seek prescription birth-control devices reflected "a great spiritual awakening" and "moral renewal" sweeping the nation.

That same day, 18 major religious leaders stepped onto the political stage in Washington, condemning the president's budget in unusually harsh and moralistic terms.

The budget, the churchmen said in a statement, showed a nation "intent on a selfish and dangerous course of social stinginess and military overkill."

The two incidents are manifestations of an intriguing subplot of the Reagan administration, a debate between the president and his critics over the morality and spirituality of his policies.

Not since the Vietnam war and the civil rights movement have churchmen been so involved or played such a key role in the dialogue over public policy.

This moralizing debate stretches across the whole range of domestic and foreign policy, from Reagan's budget cuts to unemployment, and from the effects of his tax cut to the defense buildup. The domestic side of this debate has sometimes been described simply as "the fairness issue."

An early example of the new mixture of religion and politics came last year, when U.S. Roman Catholic bishops issued a draft "Pastoral Letter on Peace and War" challenging the U.S. strategy of nuclear deterrence.

It escalated as many religious groups called for a nuclear freeze, and questioned military aid to Latin American countries.

Each side has attempted to claim moral superiority in arguments that go to the heart of the Reagan presidency: over war and peace, human survival and the basic fairness of administration policies.

When Vice President Bush toured Europe last month, for example, he argued that the administration's proposal to eliminate all medium-range nuclear missiles from Europe is "the strong moral position." When Secretary of State George P. Shultz recently appeared before a Senate subcommittee he criticized "churchmen who want to see Soviet influence in El Salvador improved."

March 8 was an important point in the battle, significant for what was said, who said it and where.

Reagan's speech attracted the most attention and controversy.

Henry Steele Commager, the distinguished historian, said:

"It was the worst presidential speech in American history, and I've read them all. No other presidential speech has ever so flagrantly allied the government with religion. It was a gross appeal to religious prejudice."

Most politicians, presidents included, have always liked to suggest that they are on the side of the angels. Theodore Roosevelt explicitly called the presidency "a bully pulpit" for moral leadership.

On the other hand, some presidents have shied away from making grandiose moral claims for their positions.

During the Civil War, Abraham Lincoln wryly observed that the North and the South claimed God's backing and "both may be and one must be wrong."

In his Orlando speech, Reagan went at the moral issue head on in urging church figures to oppose the nuclear freeze, which is supported by most major Protestant denominations and the three wings of U.S. Judaism, and to support increased military spending on moral grounds.

"In your discussions of the nuclear freeze proposals," Reagan said, "I urge you to beware of the temptation of pride--the temptation blithely to declare yourself above it all . . . to ignore . . . the aggressive impulses of an evil empire, to . . . thereby remove yourself from the struggle between right and wrong, good and evil."

Preaching "must be determined not by the policy of any political administration but by the basic teachings of the Bible that all Christians must work for peace with justice," said the Rev. Ronald D. Sisk, a Southern Baptist leader from Nashville.

"The president has every right to oppose a nuclear freeze, but he has no right to stigmatize those who disagree with his brand of 'civil religion' as succumbing to the 'temptation of pride,' " said Rabbi Walter S. Wurzburger, president of the Synagogue Council of America.

Reagan's speech was delivered to a gathering of evangelicals, a largely conservative group sympathetic to Reagan. Attempting to shore up his base among "social-issue conservatives," the president has been courting evangelicals and fundmentalists in recent months.

In late January, for example, he gave a highly charged speech to religious broadcasters in which he urged the nation to "face the future with the Bible" and pledged unremitting support for constitutional amendments that would ban abortion and permit public school prayer. He recently met privately with Moral Majority founder Jerry Falwell, a frequent White House guest, for 70 minutes.

"You invite the types of people to meet with you that you feel most comfortable with, and that's what he's doing," said Moral Majority Vice President Cal Thomas.

Peter Hart, a Democratic pollster, said he thinks this is bad politics. "Reagan is going back and trying to cover his political base. The more he does that, the more he opens up the middle," he said. "There's a sense of intolerance in what he's saying, and I don't think it will sell in the end."

Leaders of the so-called "main-line" Protestant groups have been largely ignored by Reagan. In their view, the president is interested only in the views of the religious far right.

"Under Ford and Carter, I was invited to the White House a half-dozen times, but I haven't been asked once under Reagan," said Kenneth L. Teegarden, president of 1.2 million-member Disciples of Christ church and one of the signers of the March 8 statement.

Other signers included elected leaders of national Baptist, Presbyterian, Methodist, Jewish, Unitarian, Quaker, Church of the Brethren and United Church of Christ groups. It was also endorsed by Ron Krietemeyer, director of the domestic social development office of the U.S. Catholic Conference.

The statement, delivered at a news conference in Washington, was an unusually harsh attack on Reagan's economic and military policies that suggested that the president lacked compassion and a sense of justice.

Calling the federal budget the government's "most important moral statement," it said Reagan's budget rejects "the rights of the poor," "the rights of the unemployed" and the "rights of all human beings to live their lives in peace and security."

The budget, it said, "continues the policy of using unemployment as the principal weapon to fight inflation" and "equates peacekeeping with firepower and thereby increases our insecurity as more and more destabilizing weapons systems are added to an already bloated arsenal."