We are now in the final moments of the greatest television presidency of all time. Evidence suggests the one that comes next may well be the worst.

Neither George Bush nor Michael Dukakis could ever begin to fill Ronald Reagan's shoes as a television President. Both men seem uncomfortable and adrift on TV. They must be carefully prepped, pampered and powdered for appearances, and they are preoccupied with modulating their own images.To Ronald Reagan, the camera has always been a friend, and in most of his appearances he has managed to come across as natural, friendly and reassuring. In performance at the White House - or on tour out on the road - Ronald Reagan was almost always a joy to watch on TV. That's partly because he enjoyed being there, and this enjoyment was contagious. Dukakis and Bush approach TV the way a dog approaches a bath.

In the final months of the Reagan presidency, Gipper sightings have taken on a crazy new luster. You never know quite where Reagan will pop up next. He's like Elvis. Or E.T. He's become a beloved folk character, more of a TV star than ever.

Just how much Ronald Reagan will be missed became even more apparent recently when Reagan showed up in the broadcast booth at Wrigley Field to call play-by-play at a Cubs-Pirates game and to clown around with veteran Cubs announcer Harry Caray.

Two endearing old hams had a high old time in the booth. "All right, Palmeiro, he's batting left-handed," said the President. "There's the pitch and a foul ball."

"Don't worry about foul balls, Mr. President," said Caray. "I'll protect you. You can come out from behind the counter now."

Backstage, when told TV lights were being set up in the booth, Reagan joshed, "I don't do television; I only do radio." He started in radio more than 50 years ago as a sportscaster. Later, in Des Moines, he would recreate Cubs games for listeners by following the results from a newsroom ticker tape.

And of course regular weekly radio addresses were always part of Reagan's politicking as President. The White House has released only still photos of Reagan making these talks, no film or videotape. The President felt even more relaxed and at home on radio than he did on TV; lights and cameras would have been intruders.

Reagan liked to invoke memories of a Democrat, Franklin D. Roosevelt, in many of his speeches. FDR ruled radio the way Reagan did television. Both men knew that an important part of the presidency was making themselves welcome in millions of American homes.

Not all of Reagan's appearances in recent weeks have been just for fun. He made a moving, eloquent farewell speech to the United Nations. CBS News televised it live. Dan Rather called it "an almost perfectly delivered address." After eight years in office, Ronald Reagan was still, incredibly, at the top of his form.

A recent PBS documentary, "The Prime-Time President," looked at ways politicians and TV have tried to use each other over the past four decades. Much was made of the way Reagan advisers cagily planted him in picturesque settings that would look good on the evening news.

Then the narrator said the Bush and Dukakis camps have learned this lesson well, that their public events are carefully staged, and that "news producers eat it up every night of the campaign."

Wrong! Every night of the campaign seems to bring a new story about how the candidates' photo opportunities are falling flat. Reagan could probably have visited a flag factory or driven around in a tank and brought it off, whereas Bush and Dukakis just look like fools.

The Reagan packagers have always had an asset that far outweighs their media acumen: Ronald Reagan. The costumes and scenery and make-up and props are all for naught if you don't have a great leading man. Historians can decide if Ronald Reagan was a great President, but any TV viewer can see he has been a great leading man.

"You know, I'm going to be out of work in a few months," Reagan joked to Harry Caray. "I just dropped by for an audition." Somehow, in some format, we have got to keep this man on television.

Reagan looked completely contented sitting next to Caray and announcing the game. Marlin Fitzwater, the White House spokesman, said later of Reagan, "He had a great time. I didn't think we were ever going to get him out of the booth."

Jan. 20, 1989, is going to be one of the saddest days of our lives.