IN CASE YOU'VE never seen him, rest assured that Art Buchwald looks just like you always imagined him. It didn't surprise me at all that when someone pointed him out recently he was short and wearing a rumpled, off-green sports jacket, journalist-gray pants and one of those knit ties cut straight across at the bottom. Chomping on a cigar--unlit, naturally--he was riding the down escalator into a hotel lobby, jabbering at a bunch of other Washington newspapermen. Then came an opportunity for a joke.

Spying a young female acquaintance on the up side, this yukster spun around and shouted, "Haven't seen you at the Vineyard this year! What happened, you have to get married or something?!" The young woman looked a little embarrassed, and Buchwald's friends shook their heads, smiling. "That Art," they were probably thinking, "what a zany guy." Then they all headed for the bar to talk about the Redskins.

Buchwald's view of Washington is equally predictable. He's adjusted well to the Reagan Administration--to Nancy's conspicuous consumption and the President's Wednesday afternoon horseback-riding, to the Stockman safety net and the Weinberger window of vulnerability. On the cover of his latest book, Laid Back in Washington, Buchwald relaxes on a Lafayette Park bench, the White House in the distance, a Smith-Corona portable in front of him. the clothes have changed temporarily to Reaganesque cowboy duds, but it's the same old Art, grinning slyly from somewhere within the folds of his paunchy face.

What does he see around him--the greatest economic revolution since the New Deal? A new posture of international confidence? A reemergence of American morality? Naah. He sees bureaucrats running seminars on wasteful office management, secretaries seducing bosses for Elizabeth Ray-style autobiographies, and PR moguls trying to sell oppressive Latin American regimes to hick Congressmen. As long as the elite gather in dark Connecticut Ave. bistros to eat lousy steaks and exchange gossip, Buchwald will be in business, for that is his Washington.

Laid Back is yet another compilation of Buchwald columns, covering events in the capital from the summer 1980 campaign to the Janet Cooke-Pulitzer Prize scandal. Though divided into unnamed chapters, the book has no obvious thematic thread. Pieces on nuclear war alternate with those on garage sales and cocktail parties. In almost every 750-word spurt, Buchwald manages to get in some downright funny lines, and from time to time an entire installment is clever. For example, no one has challenged Buchwald's claim to the invention of the MX missile-Amtrak gag, which has since become an integral part of Op-Ed page vocabulary throughout the nation. Insisting that "nobody wants to fool the Soviets more than I do when it comes to pinpointing our missiles," he proceeds with the definitive explanation of how Amtrak delays and reroutings would provide the perfect element of surprise needed to unhinge Moscow's first-strike planners.

The columnist almost always falls back on conversation to ensure a light tone and clarify his stereotypes. Congressmen Schmertz and Thyroid duel over whose rhetoric will cut more taxes, while Third World leader Bangambi complains to oil minister Ahmed that high petroleum prices are draining resources from the cause of the underdeveloped. "We shouldn't put a cut-rate price on our friendship," Ahmed responds. "The fact that we make everyone pay the same shows we respect you as much as we do the West German imperialist." The images are never complicated, and Buchwald doesn't hesitate to repeat his point for emphasis: the only way to follow politics is to laugh at it, and in the end, the trivia of day-to-day life is probably more interesting.

Granted, then, that Buchwald exceeds the minimum requirements of his job. He fills the space, as he has since arriving in Washington in 1962, and he can still provoke a har-dee-har-har from time to time. But given an opportunity to examine his work over an extended period, his ideas have a disturbing sameness. It's not just the reused one-liners, but more his failure to dig behind the cliches. His only unwaving concerns are those of Washington's upper-middle class when they examine personal relationships.

The book is dedicated to "that lady in Chicago Ronald Reagan kept talking about during the entire campaign because he said she cheated on welfare." But once underway, the author turns almost exclusively to topics like the real estate market in Georgetown, the inconveniences of the Eastern shuttle and the tribulations of a family man tending the flock on Martha's Vineyard. After a while, you're sure there's got to be something more poignant to relate than speculation about Jackie Onnasis' plans to move in next door and Bergdorf Goodman's arrival to follow. If he can't stand the other side of the tracks, then Buchwald should at least venture into a neighborhood with more modest split-levels once in a while.

In his political portraits, the author almost always settles for a snapshot, which would be sufficient for bit characters but doesn't satisfy in the case of a president. There's more to the man in the White House than a short memory and a tendency to oversimplify. Buchwald could still be ironic and point out that Reagan and his ilk follow an American dream inherently weighted towards those who are already strong over those who are struggling to survive. Instead, the columnist settles for the easier "All politicians are clowns" line. Case closed. One of the few exceptions to this tendency is his clear opposition to foolhardy American adventurism abroad, particularly in response to "raging communism." Yet he balances this point of view with a childishly xenophobic portrayal of the Soviets and Chinese, who barely grasp concepts like soap and water and uniformly adhere to their government's propaganda about the outside world.

Art Buchwald is not a bad man because he is lazy about his columns. Within his self-imposed parameters, he succeeds more often than not. But like most writing composed between a late lunch and a 5 p.m. Capitol Hill reception, his merits little more than a quick read. Skim until you find the punch-line, scan the letters to the editor for someone you know and then chuck the whole thing into the garbage. Has anyone ever cut out and saved more than one Buchwald column?