IN 1976, GOV. EDMUND G. BROWN JR. of California successfully parlayed two interviews -- one on CBS's "60 Minutes" and the other in Playboy magazine -- into a national political campaign. Even Mr. Brown's announcement of candidacy -- an informal aside to four reporters during an unrelated session in his office -- signaled accurately the unconventional campaign he would wage that year. Unconventional and successful.

His 1976 successes at the polls were all the more impressive, considering Mr. Brown's mid-March entry, a full 15 months after Jimmy Carter. Mr. Brown defeated the front-running Mr. Carter in both Maryland and Nevada. Then in New Jersey a delegation of uncommitted Democratic regulars -- whose hearts belonged to Hubert Humphrey but whose political antennae could spot a winner -- enlisted under the Brown banner and upset the Carter slate. On that same day in his home state, Mr. Brown qualified for the political record books by defeating the prospective Democratic nominee by 1.3 million votes -- the largest victory margin in the history of presidential primaries.

While Mr. Brown's voter appeal was obvious, the reasons for it were not as clear. Now, as then, the California governor defiantly resists any ideological pigeonholing. The old line used by some moderate Republicans (you remember them) -- "liberal on civil rights and conservative on property rights" -- has been thoroughly updated by Mr. Brown (and to some degree by the state he leads). He first assaulted California's Proposition 13 as a "consumer fraud" and then adopted it as his own after the voters approved it. The "liberal" Mr. Brown publicly defends the rights of homosexuals, boasts that he has appointed more blacks, women and Mexican Americans to public office than any other American officeholder, and champions solar energy and tougher auto-emission standards in the State of the Freeway. The "conservative" Mr. Brown urges a balanced-budget constitutional amendment and a constitutional convention to achieve it while eagerly conceding what government cannot do. He told us in his announcement speech, "My principles are simple -- protect the earth, serve the people and explore the universe." Under the umbrella of Mr. Brown's simple principles are also found his opposition to all forms of nuclear energy ("a technology whose lethal products last 100,000 years is not the way to boil water"), capital punishment, any increased spending for defense and a stated belief that "the economic and political doctrines which propelled us into such success after World War II are simply inadequate for the world we now inhabit."

Add to all this Gov. Brown's advocacy of the new "era of limits" he believes we are entering and a demonstrated electoral appeal to younger voters in his home state and elsewhere in the 1976 primaries and you have the admittedly incomplete and completely perplexing picture of Candidate Brown.

While Ronald Reagan and Edward Kennedy, all the time denying, appear to move respectively from the right and left of the traditional spectrum to the electable middle, Gov. Brown seems to take a position from the left, an idea from the right, trade one, and retain two more. This unwillingness to be classified on the political compass -- or to remain in a fixed position for more than 20 minutes -- makes Gov. Brown the most confounding candidate of 1980 and potentially either the joker or the wild card.