IT WAS APRIL, 1975 an Milton Kronheim, who will be 90 years old tomorrow, walked into the elevator of the Mayflower Hotel, where he lives, and spotted Rabbi Baruch Korff, the defender of and apologist for Richard Nixon. Kronheim asked if the man ahead of him was indeed Korff. When told he was, Kronheim drew himself up, reddened in the face and prepared to fight Korff on the spot. Like this column, that incident was about a handshake.

"Korff, I hate your guts," Kronheim yelled. The rabbi looked up, trying to figure out if Kronheim was kidding or not. It was hard to tell. He stood there with his fists clenched, as if he was going to fight. But men in their 80s do not fight other men. Men in their 80s who are legend in their own town do not fight with other men. Men in their 80s who have been friends of presidents do not attack little rabbis in the elevator of the Mayflower Hotel.

"Korff, you son of a bitch. I hate your guts," Kronheim yelled. "You're a disgrace to the Jews."

Korff smiled weakly, apparently afraid, sensing that Kronheim was not kidding. No one in the elevator said a word. Korff smiled and stepped out into the lobby. "I wanted him to take a punch at me," Kronheim said, by way of explanation. "I would have murdered him."

I was with Kronheim that day because I was writing a magazine article about him. He had once been the political boss of Washington, D.C., I had been told. He had run things here. he had known presidents and they had known him and he had appointed the District commissioners and the police chiefs and judges. He had controlled so many people and so many jobs that, for a while, Milton Kronheim, liquor dealer, was to Washington what Dick Daley was to Chicago - the boss. This, at least, is what I was told.

For year, I had been hearing Kronheim stories. I had heard about how he single-handedly built the liquor business in this town, combining business acumen, political clout and public relations savvy to turn Washington into something like an inland free port - almost no liquor taxes. There were stories about his influence and about his longevity and athletic ability. He played baseball into his 80s, for instance. There was even a story of how every day he would give the doorman at the Mayflower a tip on the stock market and how, when the doorman died, he was worth - you guessed it - a million dollar or so dollars. Wonderful story. Not true, but a wonderful story nonetheless.

So I went off to find this Milton Kronheim. He was then 86. I was going to find the old deals and the old payoffs and the old alliances. I was going to tell how Kronheim ran the city from his legendary company dining room, the one where he entertained congressmen, senators and anyone else of influence. I was, in short, going to find out what made Milton Kronheim tick.

He saw me in his office-warehouse in Northeast. He turned out to be a big man, powerful, looking 65 or so. He had just finished lunch with Judge David Bazelon, who is not, I think, your basic political type. And he took me through his place, showing me thousands of photographs that picture Milton Kronheim with someone famous. All of them seemed to document the legend of political power.

He talked of his life, how he started at the age of 14 with a Georgetown liquor store and then, with prohibition went into the bail bond business. A whole different Washington opened up: a speak-easy Washington, a street car Washington, a Washington so small and so tightly knit that you could know everyone. Milton Kronheim, I want to tell you, knew everyone.

I plugged away, interviewing people, asking the hard question about deals and payoffs and alliances. All I got back were testimonials. Always they said how much they loved Milton Kronheim. Alway s they told how he had helped someone with something - a business loan, a charitable contribution, the time in a very busy day, to ask about their family.

I spent hours with Kronheim himself, talking to him in his office and in the lobby of the Mayflower and, later, in his rooms. I went one day to watch him play handball. He played with men younger than himself, wearing a shirt with his age for a uniform number. He played on legs that were ghostly white and aged. He hit hard and he moved well, but he was old and I found myself worried. I found myself, I have to tell you, caring about Milton Kronheim.

Later, the incident with Korff occurred. It happened because Kronheim had accidentally shaken hands with Korff some time before and had wanted to wipe that slate clean. He shook hands with him by accident, not quite catching the name, extending his hand almost by reflex. But Kronheim did not like Korff, and regretted shaking his hand. He had to do something about that.

It is hard to think that a handshake can mean so much to a man in Washington, where uou have lunch with liars and go to the embassy parties given by killers and slap the backs of crooks. But to Milton Kronheim it did. Milton Kronheim is special.

So I wrote the magazine story and Milton Kronheim did not like something about it, and one day, when I say him in a restaurant and went over to say hello, I was warned to keep away - me and Rabbi Korff. It has been years now, but Milton Kronheim stays with me. Our paths cross from time to time and always I look away or go into another room, knowing now, of course, that what made Milton Kronheim tick was not deals or hard cash, but personality and character. He will be 90 tomorrow and there is something I want to do. In the newspapers, it's safe.