On the evening of Nov. 19, 1975, a group of Ronald Reagan's aides gathered here with him to celebrate the political campaign upon which they were about to embark. Peter Hannaford, a Reagan adviser at the time, had brought along a bottle of champagne. Before he opened it, he said to Reagan, "Governor, you've never told us if you're going to run."

It was a joke, at which Reagan laughed heartily.

Everyone knew that Reagan was running hard to wrest the Republican presidential nomination from Gerald R. Ford, and Hannaford had, in fact, written part of the official declaration of candidacy that Reagan would make the following day.

But it also was true that Reagan had left it to his advisers to reach the conclusion that he was running and to do the fund-raising and necessary organizational work. Reagan, as always, was somewhat removed from the battle and ready to announce in his own good time.

This half-forgotten snapshot of the past came to mind recently as Washington renewed its interest in one of the games the media plays with incumbent presidents, a game that might be called "sending signals."

Largely a game of chance, it also involves the skills of fortune-telling, linguistic analysis and political strategizing. It is a game that Reagan plays superbly.

All year, Reagan has been sending signals, and sending them in all directions at once.

Some see his recent militancy toward the Soviet Union and his espousal of social issues that he had downplayed as a sign he is moving to shore up his essential base before seeking reelection--although he has the nomination for the asking and usually moves toward the center when he has the right in hand.

Others see his recent praise of his loyal and hitherto invisible vice president in the wake of George Bush's well-publicized European trip as a sign that Reagan isn't running and is paving the way for Bush--although Reagan always has publicly lauded his various seconds-in-command, whether he or they were running.

And so it goes. He has appointed women to the Cabinet, which his surveys tell him is a good idea, but allowed Drew Lewis, the most politically able member of his Cabinet to leave.

His friend, Nevada Sen. Paul Laxalt, has been named general chairman of the Republican Party, but Laxalt, who thinks Reagan will run again, has been given no commitment of a reelection candidacy, and no Reagan fund-raising machinery has been set in motion.

Reagan has come around on the jobs bill, politically smart for a president seeking reelection. He has stepped up his criticism of the nuclear freeze, which is not. He deliberately failed to include in his State of the Union message a statement expected by Republican senators declaring that it would take more than four years to accomplish his goals.

Then he gave a guarded version of this theme in a late-night speech to a conservative political action conference. He has developed a carefully balanced non-answer to those who ask him whether he will run again.

It is no secret in the White House that the president is amused at the way reporters take this non-answer and run with it in the direction that suits their predilections.

This reporter is on record with the opinion that Reagan will decide not to run again.

This may be right or wrong, but it is evident to those closest to the president that Reagan is telling the truth when he says he has not made up his mind.

One close adviser says the president realizes that he is the political beneficiary of uncertainty, and adds that what Reagan has to do to be a successful one-term president also is what he needs to do to be an effective candidate for reelection.

In his salad days as a conservative politician on the hustings, Reagan liked to say, "They told us the truth the other day in Washington, hoping we wouldn't believe it."

And we often don't.

In this game of sending signals, the president is in the enviable position of benefiting from the kind of simple, uncomplicated answer that so often gets him into trouble.

The truth is that he hasn't made up his mind.

Peoria Mayor Richard Carver is known to have "expressed interest" in the intergovernmental relations job in the White House when Rich Williamson leaves. Carver, an outspoken Republican, is considered to be one of Reagan's favorite mayors.

White House spokesman Larry Speakes responded last week to a question about whether deputy chief of staff Michael K. Deaver and presidential assistant Richard G. Darman would leave by saying, "Rubbish, rubbish, rubbish." When a reporter observed that he had used three rubbishes for two aides, Speakes replied: "Two for Darman. He needs all the help he can get."

Reaganism of the Week: Speaking to students at the Epcot Center in Orlando, Fla.: "I recently learned something quite interesting about video games. Many young people have developed incredible hand, eye and brain coordination in playing those games. The Air Force believes these kids will be our outstanding pilots should they fly our jets."