OF COURSE Jimmy Carter doesn't want John Anderson in the debates. Mr. Anderson gives him political problems, so why would he? Mr. Carter probably also doesn't want a lot of other things in any debate that may take place between himself and Ronald Reagan. He probably doesn't want Mr. Reagan to look very good or the discussion to turn for long on his own and his administration's particular weaknesses or the format to make him and Ronald Reagan look like well-matched, may-the-best-man-win equals, but rather, like responsible incumbent and reckless, pesky challenger. But sometimes you don't get the things you want, and the question then is: what do you do about it? That's where Mr. Carter comes out looking frightened. In his effort to keep Mr. Anderson from seeming "presidential," he manages to look unpresidential himself.

It is being said by Mr. Carter supporters that he had no choice, that it would be politically self-destructive for him to let Mr. Anderson get the boost of a three-way TV debate. But what is the alternative? It is to be seen fearfully and disingenuously trying to deny Mr. Anderson a place that the League of Women Voters has offered him alongside the other two candidates. Let's at least get this much straight. Mr. Carter is not trying to stop Mr. Anderson from robbing a bank or murdering small children or poisoning the nation's water supply or developing an atomic bomb of his own. He is simply trying to stop him from getting the exposure and the opportunity to seem a serious candidate that are built into the League's invitation. It is the prospect and the way it plays against the president's self-interest of which Mr. Carter's mentors are now saying: yes, we know how it looks, but what else could we do?

Well, we have an answer to that. It begins with the word, Relax. There is no reason to get extravagantly high-minded about this. What we are witnessing, as always in these debate-arguments, is a normal political jostling for advantage. But Jimmy Carter has a way of getting a bit uptight and nasty and going beyond normal jostling when someone gets in his way. And so the refusal to appear at the Sept. 21 event if John Anderson is allowed to be there has been accompanied by the predictable excesses. The implications of the president's complaints about the press coverage Mr. Anderson is getting are weird. As he should know better than anyone, the rise from political obscurity to national fame is not and should not be strictly determined by how closely connected a candidate is to established political institutions. Mr. Carter also resents the fact that, as he puts it, "He and his wife hanpicked his vice presidential nominee." Who picked Fritz Mondale? If it was the Democratic convention of 1976, then how come all those would-be candidates were trotting down to Plains to be looked over? We even think we remember something about both Rosalynn Carter and the president's mother helping to "pick" the current vice president.

There are a lot of people in this country, we think, who are against the president or at the edge of being against him for reelection who would really like to be for him. These are people who desperately want Jimmy Carter to convey something more masterful and ressuring and self-confident -- in fact, presidential -- than he has been showing them in the past couple of years. That kind of a fellow would simply have smiled and said: Hell, bring them all on -- I can do it . . . If they are crazy enough to want this job in the first place they can't present much of a threat. But there isn't that much ease in the president just now. And the lack of it is hurting him.