In recent days the Rev. Jerry Falwell has been all over the place. Turn on your television set and there he is, a cherubic Friar Tuck of the Right who smiles benignly as he smites his foes hip and thigh with biblical fervor. Pick up your newspaper and he fills a full page with "an open letter from Jerry Falwell." Travel around the country, on business or pleasure, and you're almost certain to notice he's been there speaking out before you.

Last week alone he logged some 10,000 miles crisscrossing the country. His schedule took him from his Liberty Baptist Church in southwestern Virginia to appearances in Los Angeles and Orange County and northern California and Chicago and Detroit, among other stops. His words resound over the nation's airwaves. You can hear him on some 500 radio stations and about 400 television outlets--and that's just the sound coming from his programs, not those from his current burst of around-the-clock interviews, whether local or network, daytime or prime time.

For Falwell to be in motion is not new. As head of the self-proclaimed "Moral Majority," he constantly moves about the country preaching his old-style fundamentalist religious message with a new national political twist. But his recent labors do represent something different, and significant.

His present formidable travels across the nation have a single, well-orchestrated, well-financed political purpose. As he would put it, he's rallying support for the president's nuclear arms policy of "peace through strength." Others, less charitable, would say he's selling the bomb.

Either way, he has become a factor in the rising clamor over the continuing great debate of our times: how best to control nuclear weapons.

A certain tension about mixing politics and religion always has been with us in America, and yet the intermingling of the two always has existed here. From the earliest days of the Pilgrims, when Cotton Mather railed against witchcraft with fanatical ardor and Jonathan Edwards turned against the Enlightenment sweeping Europe and zealously preached a harsh brand of evangelical moralism known as the "Great Awakening," the role of men of the cloth in national politics has been a long and continuing one.

The idea, which one hears of late, that such ministers as Falwell should stick to the pulpit and address questions of God instead of straying down into the political pit and addressing current issues of man is, of course, absurd. He has every right to express himself, to create controversy if you will, as did Father Coughlin, the right wing "radio priest" in the '30s, and the more recent examples in the '60s and '70s of the Rev. Martin Luther King Jr. and the Berrigan brothers. They spoke out strongly on national questions of civil rights and war and peace and stirred no less controversy then than Falwell does today.

What distinguishes Falwell is his association with the secular head of the nation, the president.

Slightly more than two weeks ago, on March 15, Falwell met with Ronald Reagan for an hour and 10 minutes in the White House. A key Falwell aide tells me they discussed the nuclear freeze movement and the politics of the situation facing the president.

Reagan, according to this account, remarked that Falwell was the only major conservative minister speaking out in opposition to the nuclear freeze. He mused aloud about why it was so difficult for him to get his peace-through-strength message across to the country. Falwell replied that one of the problems was the extremely complicated nature of the subject; the president's case hadn't been boiled down into language the average citizen, the farmers and laborers of America, could understand. If the president could supply him with such language, and the official facts and figures to back them up, he, Falwell, would be proud to carry that case to the public.

The president then called in an aide and instructed that such material be prepared for Falwell.

Several days later, Falwell returned to Washington. He was given a briefing by National Security Council aides, accompanied by charts and graphs, and written material making the president's case "in laymen's language" about the Soviet military threat and America's presumed fading military strength.

Since then, Falwell has been off and running. His organization has reproduced the president's written material in even more simplified language. It is being distributed to hundreds of thousands, perhaps millions, of Americans. His full-page ads running in papers nationally tell citizens:

"We cannot afford to be number two in defense! But, sadly enough, that's where we are today. Number two. And fading!"

And he goes on to say, in language that directly impugns the loyalty of opponents, specifically duly elected representatives of the people:

"We have a president who wants to build up our military strength. But he is catching it all from all sides. The 'freeze-niks,' 'ultra-libs' and 'unilateral disarmers' are after him. He and the loyal italics added members of Congress need to know that you are with them."

His electronic audiences hear him describe what the president "told me" and how the National Security Council "briefed me." He asks listeners if they are going to take the word of the president and the secretary of defense, as relayed through himself, or others? And he makes dark allusions to those advocating a nuclear freeze having "links with the Kremlin."

Falwell's aides say they are being "overwhelmed" by the favorable public response to his appearances. They believe he is having "a very significant effect" in transforming public opinion from a pro-freeze stance into one backing the president's views.

If so, the Rev. Jerry Falwell will have become something more than a crucial factor in our great nuclear arms debate. He will have written a new, potentially fateful chapter in the story of church and state relationships in America.

Note: In a recent column about James G. Watt and his stewardship of the Interior Department, I incorrectly described Gifford Pinchot as one of Watt's notable predecessors in that job. Pinchot, one of the great conservationists of the century and a staunch ally of Theodore Roosevelt, never was interior secretary. As I was pleasantly reminded in a phone conversation by someone who once served with Pinchot, in the late 1890s he was confidential agent to the interior secretary advising about the state of America's forest reserves and then became chief of the U.S. Forest Service (and later was a strong governor of Pennsylvania). My old American history professor at the University of Wisconsin, the late Howard K. Beale, who made "T. R." and his times his life's work and a was a fervent admirer of Pinchot, would blush with embarrassment at my stupidity, as I now do here.