THIS IS THE way I heard the story. I heard that years ago the vending machine people held their convention in Washington sometime in the late summer or early fall. They moved their machines into the D.C. Armory, the next best thing the city has to a convention center, and opened for business. A heat wave moved in. The fans were turned on. The weather got worse. The chocolate bars melted out of the machines and the vending machine people have not been back since.

I heard that story a couple of years ago when I was reporting a story I never wrote. My idea was to spend a week in a major Washington hotel and write a series about it - sort of a nonfiction version of the best seller. "Hotel." The hotel I chose was the Sheraton Park; the city's largest and a major convention facility.

I did the usual things. I followed a maid around and learned what she did and I spent time in the kitchen learning how you cook for 5,000 and I tailed the hotel engineer, learning about air conditiong and laundry and elevators. It was an interesting time in the hotel. The Moose were in convention there and the International Monetary Fund was about to meet there and so a lot was happening. As a result it was not until late in that week that I got around to the sales staff. I should have started there first.

It was then that I learned about conventions. I learned about how the sales staff was selling conventions as much as 10 years in advance. I learned how they courted organizations officers for years, knowing, say, that this year's secretary would be president in five years and in position to choose the convention city. They remembered his birthday.

It is all something of a vague memory now, but I remembered being impressed at the amount of money at stake in the convention business. There were formulas involved, books that we kept on everyone from the Moose to the Air Force Association. Some conventions weren't worth a thing to either the hotel or the city and some were worth a fortune. There were some groups. For instance where you had to keep an eye out to stop them from cooking with hot plates in their rooms and others where there were nothing but big spenders with a penchant for room service.

The one thing you kept hearing was how the city needed a convention center. This was a partisan group but they made a good case, saying that some of the biggest conventions would no longer come to Washington. There was not enough hotel space, for one thing, but there was also no facility big enough to display lots of equipment or seat thousands of people. As a result, these people said, Washington was losing conventions to Atlanta, Las Vegas and Kansas City, to name just three cities with fairly new convention facilities.

Ever since those days, I have been something of a convention center booster. I thought the city should have one and I was pleased when the city decided to build one. I just presumed that everyone would agree - a good thing being so apparent that there would be no argument. Well, there was, and the more I listened to the other side of the story, the more uncertain I became. Some people were saying, for instance, that the convention center would never generate the kind of economic activity that would make it worth-while and amounted to something of a windfall for the City's convention and tourist and - just maybe - real estate industries.

Well, it was hard to say which side was right. I got confused. I studied the issue and I read all the stories about it and I talked to some people, but I simply could not make up my mind. I wanted to do a column about the issue, but I could not decide which side to come down on. I was still basically pro-center, but not in any fanatical way. In fact, I had my doubts.

So I wrote nothing and left matters take their course. I let others deal with the problem, make the hard decisions, have to wade through mounds of reports and projections and volumes of testimony. I held back, but, I, was satisfied that nothing was being pushed down anyone's throat - that the matter was being responsibly handled, which is not something you can always say about things in this city.

Now at the moment this is being written, the convention center appears dead because of congressional action. It's in trouble for a number of reasons, some of them having to do with a procedural vote in the house, and some of them can't lobby its way out of a paper bag. But it died mainly because a senator named Leahy didn't like the idea

Well, I don't mourn the center and I don't blame Leahy. He did what he thought he had to do. It was his job. But I have to tell you that I got mad at what happened. I got mad that a single man who lives in Vermont blocked a convention center for Washington and made the efforts of lots of people go straight down the drain. Frankly, I got mad that I had even considered doing a column about the center, forgetting that in this town you can just relax and leave to Congress. A lot of people would call that a shame, or a scandal.

At the moment, it's called home rule.