THE INDEPENDENT presidential candicacy of Rep. John B. Anderson, which had seemed to be somewhere near "struggling" on the route to "fading," has both made and had a little good news lately.

After the most recent published findings of sages Gallup and Harris, Anderson partisans definitely needed good news. The polls revealed sharp drops from a last April high of 23 percent support for the Independent in a three-way race with Republican Ronald Reagan and Democrat Jimmy Carter. Mr. Anderson, in the latest soundings, was close to dropping beneath the 15 percent level of popular support that the League of Women Voters had set as the minnimum for an invitation to the League's presidential debates.

Mr. Anderson now has a real vice presidential running mate for himself and his unity ticket: former governor and ambassador to Mexico Patrick J. Lucey. Mr. Lucey was one of the true founding fathers of the modern Deomocratic Party in his home state of Wisconsin. Most frequently associated with various Kennedy campaigns, Pat Lucey had first organized the Wisconsin Democratic Party during the time of Sen. Joseph McCarthy's greatest influence in both the state and the nation. A millionaire businessman, a liberal who had good relations with organized labor during his three successful and one unsuccessful statewide campaigns, Mr. Lucey does not bring either instant celebrity or political glamor to the Anderson ticket. But he does bring and established record of political and public achievement.

The efforts by the Carter campaign to keep John Anderson out of presidential debates has also given the Anderson campaign a much-needed lift. If the Carter folks are that concerned about John anderson's presence, this argument goes, then maybe, Mr. Anderson deserves another look.

But the Anderson campaign, which of necessity had to devote a great deal of its time and energy to winning ballot placement in all the states, has failed to define the Anderson difference. Mr. Anderson has of late run more like a pragmatic remainderman, emphasizing only that he is not Ronald Reagan or Jimmy Carter, than like any authentic third-party candidate with a clear message.

It is a long time since the gun owners' confrontation in New Hampshire, where there was an Anderson difference, and since the Iowa debate, where he explained how the Republicans would balance the budget, stop inflation and increase defense spending: "with mirrors."

The Anderson campaign has won, at last count, ballot position in 39 states, after court fights in Kentucky, Ohio, North Carolina, Maine and Maryland. But the theme and the difference have been missing. It is almost as though the encouraging polls of last spring altered both the candidate's and the campaign's self-perception and the campaign became too careful, too concerned with winning, too conventional. One dilemma Mr. Anderson and his campaign (which has undergone some major shakeups in leadership this week) must face is that the only chance of winning John Anderson might have in 1980 almost surely requires that he forget about winning.

In an interview with The Post ealier this year, Mr. Anderson spoke of his admiration for the late Adlai Stevenson and for his having "the courage of his convictions." Now is the time for Mr. Anderson to define himself and his candidacy beyond the obvious fact that he is neither Ronald Reagan nor Jimmy Carter.