The more things change (I was reminded while parsing the Haig-speak of "a senior administration official" on the new "global" approach to Central America), the more you find yourself digging into journalistic mini-archives and discovering how much they remain the same.

The "global" approach would seek to get us off our "myopia" with El Salvador by thinking big. The way to avoid the "creeping escalation" of Vietnam, the official said, is to talk to the Soviets--and not just about El Salvador or the Cuban/Nicaraguan connection. You put almost everything on the table: Soviet "vulnerabilities," in Poland, in Afghanistan, economically at home; a wide range of unspecified American "political, economic and security assets," including capabilities in areas of "strategic importance" to the Soviets. You toss in arms control, trade, technological transfer, the value of d,etente. And then you cut a deal.

The way you spell relief from El Salvador, in short, is L-I-N-K-A-G-E, the controversial doctrine of the essential interconnection of events and great power concerns that first came to public attention in the early Nixon days. Its history is worth examining now that it seems to be re-emerging, a little blurry but recognizable, in public statements and background briefings by Al Haig.

It figures, actually, when you examine the historic linkage, so to speak, of the theory of linkage. A yellowed clipping recalls an interview with Nelson Rockefeller on March 20, 1968. He had a way out of Vietnam, "not in continued escalation of the U.S. military effort but in a search for a wider Asian accommodation. . . . We would hope to increase the interest of the Soviets, among others, in a solution that would neutralize that part of the world."

Rockefeller's principal (if not his only) foreign policy adviser had been Henry Kissinger. A little less than a year later, on Feb. 4, 1969, President Nixon made "linkage" official U.S. policy in a letter to his secretaries of state and defense, and the CIA director:

"We must recognize the Soviet Union has interests," he wrote. "In the present circumstances we cannot but take account of them in defining our own. I am convinced that the great issues are fundamentally related. I do believe that crisis or confrontation in one place and real cooperation in another cannot long be sustained simultaneously."

The man who drafted that letter, and who by then had become Nixon's national security adviser: Henry Kissinger. Two days later Kissinger introduced linkage into the language--in a press conference reference to "the linkage between the political and the strategic environment."

Right about that time, Kissinger recalls in an excerpt from his second volume of memoirs published in Time magazine, he hired (after just one interview) a "rough-cut" Army colonel as his military aide. After only a year, the colonel became his "indispensable" deputy who "acted as my partner."

That would be the incumbent secretary of state: Alexander Haig. Last weekend Haig let it be known that President Reagan's policy for dealing with El Salvador is "to harness, and we have been, the full panoply of political, economic strategic assets of the United States to deal with this problem in Moscow, in Havana, in the regional context of the Organization of American States and in El Salvador."

Without laboring the genealogy, there is in this language a certain rhetorical resemblance to earlier formulations. Whether Henry Kissinger would acknowledge parentage is something else. Earlier this year, in a biting critique of the administration's policy on Poland, he recalled that "linkage was the watchword" in the early Reagan days, but that its key premises were "being cast overboard" by the continuation of arms control talks and the absence of really tough sanctions.

Reached by phone at Palm Springs, where he is recuperating from heart surgery, Kissinger declined to talk on the record about the chances for effective use of the linkage doctrine in Central America. But his reference to his own previously published works suggested some serious doubts.

Kissinger's first rule is that "linkage" is not so much a "decision" as a "reality." Thus, if the United States is losing out in Central America, the Soviets (who disclaim responsibility in any case) could not be expected to cooperate; and if the United States is winning, there's no need for linkage. A second Kissinger requirement would be a demonstrable American readiness to act forcefully: to suspend arms control talks, cut off grain, intervene militarily in the Caribbean.

On both counts, linkage failed in Vietnam--but not, Kissinger would insist, because it wasn't tried. Only a clearer view of each side's calculation of assets and vulnerabilities will tell whether it will work any better this time around.