Since becoming president, Jimmy Carter has made his mark on the nation and the world. He has brought peace (up to a point) to the Middle East. He has shown the Russians (up to a point) who is boss. He and his wife have convinced millions of married couples there is nothing wrong with holding hands in public. And lots of other good stuff.

But the president, diplomat/statesman/tough politician that he is, may have met his Waterloo here in Potomac River City Right where a lot of I-told-you-so-types predicted it would happen.

What the president did was tackle the sacred cow of an opponent who, when aroused, can match Ho Chi Minh for staying power and make Attila the Hun look like a sweetheart. The sacred cow is, of course, the free-parking space. The opponent is, of course, the typical federal employe who had one until Carter took it away.

Last year, in a move designed to purify the air, uncongest the highways and save oil by forcing car pooling, Carter abolished most free parking in government. With a stroke of the pen, Carter told federal agencies to start charging people the same rates they would pay if they had to park in nearby commercial lots. Fearing rebellion, advisers convinced the president to make the free-to-pay transition in easy stages. Charge them half the rate in 1980, they said, then ease in full parking fees in October 1982 when folks have calmed down. It seemed like a good idea at the time.

As it turned out, however, federal workers took to the trenches, the picket line and finally to the courts. In retrospect, Jimmy Carter never had a prayer.

Thousands of federal employes picketed the White House protesting the imposition of paid parking. A new bureaucrcy sprang up in government to handle allocation of parking spaces and stickers and to collect money. Various groups of workers got together to form committees asking for exemptions from the pay parking order because it was, they said, unfair and arbitrary or because public transportation to their worksites was nonexistent.

The American Federation of Government Employes union got into the act and took the president to court. To make a long story short, they won the first round here the other day when a federal judge ruled that Carter couldn't take away free parking without the advice and consent of the Congress. (Congress, by the way, has talked about instituting pay parking for senators and representatives but hasn't gotten around to it yet).

To add insult to injury, federal workers who are on the verge of getting their free parking restored also want their money back. Rates vary, but the typical U.S. worker now pays around $12 per month for a space. Multiply that by 300,000 parking spaces, times nine or 10 months, and you are talking about a sizable rebate.

The Carter administration is between a rock and a hard place on this one. Unless they decide to make a federal case out of it, free parking could return. And the government could be forced into a lengthy nightmarsh process of refunding money to thousands of people, including many who have died, retired or moved away from their old parking space.

On the other hand if Carter gives in on this one, there are a lot of people who do not work for the government, who pay a lot for parking, who will see him as a punching bag for the bloated bureaucracy he came to town to deflate. And there are many civil servants who don't drive to work, or maybe who can't afford cars, who might ask what the government is going to do for them if it is going to return to subsidized parking? Should Uncle Sam issue Metro passes of bus tokens to employes who don't drive to work? What if you have to drive but can't get a free parking space. Does Uncle Sam dispense free gas to commuters? Some readers have suggested it.

The next step is up the president. He can decide to fight what could be a long, costly land war against the bureaucracy's tough, battle-hardened parkers. Or he can cut his losses, the like many presidents before him, accept defeat with honor at the hands of the federal establishment that was here long before he arrived and will be here after he is gone. Nobody ever said being president would be easy.