Richard Nixon is back, standing tall on the cover of Newsweek and in Ronald Reagan's White House. The "newest" Nixon has "rehabilitated himself, after a fashion," says the headline inside the recent issue of the magazine, "and he is expanding his influence on the White House." An anonymous White House "senior aide" is quoted as saying, "There's tremendous respect for him around here."

That's very large-minded on the part of the White House crowd. I am not talking about the ease with which not only the Reagan White House, but a lot of other people apparently forgive or forget what it was that made Nixon the only ex-president who required a presidential pardon for his peace of mind. It is enough to note that in an accompanying interview, Nixon quotes Winston Churchill in his defense: "Churchill's study of history showed that great leaders more often stumble on little things than on big things." The "little" things he was talking about (burglary, obstruction of justice, perjury, abuse of power) go under the heading of Watergate. There is no "newest" Nixon.

But the old Nixon retains a certain mastery of geo-politics. And if Reagan had been listening to Nixon he would not have launched his Strategic Defense Initiative with anything like the sweeping claims he made for it. He would not be making such a big deal about international terrorism. He wouldn't have called Qaddafi a "mad dog." He would be "anticommunist" in the "somewhat more sophisticated way" that Nixon claims to be.

Nixon, while engaging in no end of self-serving commentary, makes no particular claim of significant contributions to Reagan's thinking. "I talk to him quite regularly," he says, but "usually he calls me from Camp David, usually after he has had one of these, you know, tough decisions. For example, he called me after the Libyan business, and we chatted a bit about it."

Had Reagan called ahead of time, Nixon apparently would have approved of the air strike on Libya: "I think we did the right thing at that time." As to what we should do now, Nixon is at best ambivalent. Taking a lesson from Vietnam, he would argue now against anything short of "massive" bombing: Vietnam tells us that "gradual escalation does not bring down a fanatic." But he sees a public-relations problem with bombing and appears to incline toward "the most obvious" option of an economic and diplomatic quarantine.

Leaving aside the question of exactly what to do about state-supported terrorism as practiced by not only Libya but Syria and Iran, Nixon had sharp words about the Reagan administration's penchant for discussing its plans out loud. He cited Reagan's implied threat to do to Syria and Iran what he had done to Libya and the State Department's subsequent clarification that no such plans were under consideration. "A great mistake," says Nixon, adding: "Never talk about what you are going to do, but don't tell them what you are not going to do." He takes a whack at Secretary of State Shultz for publicly advocating a "covert capability. . . . I would respectfully suggest, develop it but quit talking about it."

Nixon had equally sensible advice about the proper approach to the general problem of terrorism: "Cool the rhetoric. . . . People who say they want to die and go to heaven and Allah or whatever, they like all that" sort of talk.

Nixon is very nearly contemptuous of "hawks"' who cling to the dream of nuclear superiority over the Soviet Union -- a dream written into the Republican platform at the convention that first nominated Reagan for president. It was a dream very much a part of Reagan's strategic thinking when he came to power. "Not possible," says Nixon: "Never going to happen."

As for Star Wars, Nixon sees no possibility of an effective nuclear defense until "far into the next century" and warns against "broad, general statements that what we are searching for is a way to make nuclear war obsolete." That is precisely the word Reagan used when he unveiled his SDI. Nixon wishes it were possible, but believes "it is not going to happen."

He is equally scornful of the notion that democracy, American-style, can be made to work in a lot of places around the world where the Reagan administration says it wants to restore democracy, such as Haiti and the Philippines. "Get all that nonsense out of your head," says Nixon, "because it won't work."

That may be a bit harsh. But much of what Nixon is saying makes him out to be a veritable voice of reason by comparison with an administration over which he is supposed to be exercising increasing influence. It is enough to make you wish that the respect of the Reagan people for Rchard Nixon was a little more "tremendous." He talks more sense than they do on the one subject, foreign policy, on which it might be claimed he is entitled to a respectful hearing.