John Glenn's 1983, earthbound view is worth examining, and not just because he is prominent among the winter-book favorites for the Democratic presidential nomination next year. Glenn's views, set forth in a recent interview, are interesting because, more often than not, he is found in or around his party's middle ground, taking positions and singling out the issues that are likely to wind up in the Democrats' campaign bill of particulars against the record of the Reagan administration.

Glenn's foreign policy gives high priority to the world economic crisis. This means first fixing the U.S. economy-- "We're the biggest engine on the international scene." That means getting interest rates down, which means "getting control of the federal budget," which means forgoing the third year of the Reagan tax cut, just to begin with. He would have passed up last year's cut as well.

Glenn sees little room for budget economies sufficient to make a big dent in deficits in the years ahead. Although defense spending is by no means sacrosanct, he doesn't think it offers much room for deep cutting.

He doubts the need for the MX missile, and would abandon the whole idea of Ronald Reagan's Rapid Deployment Force as a waste of money. "It's the only time in military history I know of where we have proposed putting the supply lines out ahead of the troops and expecting the stuff to be there when the war starts," he argues. He sees the U.S. Marines (he was one, after all) as the logical RDF, capable of moving not just to pre-positioned supply dumps (the logical first enemy target), but "to where the combat is."

And that, to Glenn, doesn't mean anywhere and everywhere. "We can't take on the whole world by ourselves," he says. Therein lies the key to the Glenn approach to national security, and to ultimate defense economies: a gradual retailoring of U.S. commitments to fit U.S. capabilities, with a whole lot more burden- sharing and mission-sharing by our allies.

Glenn had a hand in working out compromise legislation to freeze U.S. troop levels in Europe by way of blocking a proposed reduction last year. But he would aim toward an eventual drawing down of U.S. forces in Europe, arguing that if our NATO allies want us to defend their vital oil interests in the Persian Gulf, they should at least take up more of the job of defending their own territory.

While by no means belittling the Soviet threat, he thinks current measures of relative U.S.-Soviet military strength are basically flawed. "We look at these little boxes that say the Soviets have so many bombers and we have so many less, and therefore we should have X number more. Yet bombers don't fight bombers. They go up against certain defense capabilities." A more practical portrayal of relative strength and weaknesses, he suggests, might reveal a more realistic reckoning of the U.S.-Soviet balance of forces.

Glenn would put a lot less money into military aid to protect Third World nations from "external" threats and a lot more into economic development to reinforce poorer nations against "internal" unrest and upheaval--and not just because he thinks the external (communist expansion) threat is overdrawn. His concern for the economic welfare of Third World nations has as much to do with the markets they provide for U.S. exports (and the jobs they provide in the United States) and the degree to which they are our sole source of vital raw materials.

Even when Glenn may be wrong, he comes across as reasoned. He knows quite specifically why he thinks Ronald Reagan lacks a "straightforward" foreign policy. He has identified with some precision the very sort of zigzagging by Reagan--on Taiwan, on the European-Siberian pipeline, on Camp David--that Reagan held up as Jimmy Carter's greatest weakness.

A Glenn campaign may not electrify. To the extent that it informs and defines the developing presidential debate, it will not be in terms of ideology or grand design. That's not John Glenn's style. Rather, what Glenn already has at hand is a manual, however imperfect or incomplete, on how to fix things he thinks need fixing.