A former foreign correspondent I know likes to tell the story of a columnist who made the mistake of visiting the Vietnam War he so loathed. The man got off the plane full of conviction and plunged right into confusion. Almost instantly, he became overwhelmed with details, nearly losing his perspective and convictions in a jungle of briefing books. Only when he returned home could he once again see the forest that had become trees in Vietnam.

And so it is, I fear, with Walter Mondale. The man suffers the fatigue of experience and expertise. He has been a senator, vice president and party leader for so long that for every hand there is another hand. His instincts are dulled, and he has the ideological pallor of the stereotypical bureaucrat. There are no issues; there are only problems.

Take, for instance, the recent bombing of the U.S. Embassy in Beirut. Mondale now says it exemplifies Ronald Reagan's lack of leadership, his unwillingness to discipline subordinates, his inability to learn from either the first or second terrorist bombings of American installations in Lebanon -- all that and more. And the "more" quickly followed. Reagan likened delays in making the embassy secure to renovating a kitchen, and when that landed like the proverbial lead balloon, the president reached for his Jimmy Carter doll and gave it a punch. Mondale punched back.

But not at first. Instead, he once again mistook authority for the flag and rallied to it. He said, "I don't want to use this occasion to talk politically" -- and then added that he would support whatever reasonable plans the president had to retaliate. This was Mondale at his instinctive worst, the insider with such an appreciation for the complexity of things that he had no capacity for outrage. His basic emotion was empathy. After all, he was once an insider himself.

If this were an isolated incident it would hardly be worth mentioning. But Mondale, you will recall, was tardy in denouncing the Vietnam War -- and did so on the ground that it was unpopular, not wrong. He has called this the worst mistake of his public career and explained it by saying he was close to Hubert Humphrey, who was, after all, Lyndon Johnson's vice president. This is loyalty twice removed, and loyalty to fellow politicians, not to constituents who were being blown to bits in Vietnam.

Mondale was similarly tardy in calling for a Marine evacuation from Beirut. Once again, loyalty and details overwhelmed him. It's only a guess, but it's likely Mondale was listening to his friends in the pro-Israeli lobby who were pushing for the Marines to stay. He knew too much, saw so many sides of the picture that he lost sight of the picture. In the end, 241 Marines were killed in a terrorist bombing.

Experience and expertise do not invariably dull the instincts and mute outrage. Reagan, for instance, has been able to retain the pose of a government outsider even though he is the head of the government itself. It's a sham, but a charming one that's popular with the voters, and his instincts generally remain sharp.

House Speaker Thomas P. O'Neill never pretends that he is not in government service, but he is nevertheless capable of purple outrage. On the same day Mondale could summon up no outrage, the speaker voiced his consternation: "I can't understand. It looks like a repeat of what happened to our 241 Marines."

There are many, I know, who say that both the latest Beirut terrorist bombing and Reagan's clumsy attempt to either rationalize or scapegoat it made for his worst political period and Mondale's best. Half of that is true. Reagan showed neither leadership, taste nor an ability to learn anything at allfrom experience.

Mondale, though, initially showed his worst side also. And while he subsequently recovered and went after the president on the quite legitimate issue of the bombing, the suspicion remains that everything he said afterward was as scripted as a Reagan press conference. For someone with Mondale's record, that was damaging. Better late than never is not always the case. As he proves time and time again, in politics they are often the same thing.