Once again the word from Washington sounds familiar. The president stands in trouble.

Proof lies not in the views of the pundits. The hard evidence comes from the people who are supposed to make us laugh, and do. Why they should be the ones who make the most telling case, rather than the oracles of the press or (hopeless thought) what passes for the formal opposition, i.e. the Democrats, poses a different kind of political question. Of which more later.

At some point early in his presidency each chief executive finds the collective wisdom of the Washington insiders, journalistic branch, dramatically shifting to form a new consensus about him. Whereas only days or months before the latest White House occupant was being hailed as the greatest leader since Caesar, suddenly it's the woeful nature of his performance that commands press comment.

You know: from the bright sunshine of the New Era he's traveled back into the dark and gloomy presidential present.

Even in Washington, where every puff of wind swirling around the monuments momentarily becomes a political tornado, these changes in sentiment aren't taken too seriously. Outside of the capital, I'm convinced, people pay no attention to them. If they notice at all, it merely confirms their beliefs about the fickleness of political thought here.

Not so the commentary of the humorists. They really count. Let one among them with any national following begin to poke fun at the chief executive and you can be sure trouble brews. Beware when a Johnny Carson starts lampooning him before late-night TV audiences. Be doubly watchful when more than one rises to ridicule our leader. But let the two most celebrated among their ranks bracket him and then fire for effect, as they say in the artillery, you know it's time for him to race for the presidential shelter.

That's just happened. I refer to the latest offerings of Art Buchwald and Russell Baker. They have zeroed in on their target, devastatingly.

Mark the dates. Sunday, Sept. 13, 1981, Buchwald on "Ronnie's Retreat":

I went to California and had a great time. I went horseback riding and slept late and worked on a farm and fed the cattle, and fired 14,000 air controllers.

We had a lot of fun. I cut brush, cleared out trees, hiked with my best girl, Nancy, and shot down two Libyan airplanes. I was sleeping when we shot them down and my best friend Ed Meese didn't wake me up in time. But it was fun hearing about it . . . .

Wednesday, Sept. 17, 1981, Baker on "Dishing It Out," following the news that Nancy Reagan has taken $209,508 of the $822,641 given by millionaires to redecorate the White House and has bought various pieces of china averaging just under $1,000 per place setting:

Naturally the president didn't notice the new dishes right away. He was too preoccupied with the day's work when he sat down at the table.

There were so many budgets to be cut. The military budget--there was a nightmare. It was a lot tougher than cutting off the welfare chiselers. Good progress being made there. A new federal ruling that anybody on welfare who owned more than $1,000 worth of household goods would be cut off ought to squeeze the rascals away from the public trough . . . .

Thursday, Sept. 18, Buchwald explaining to his young nephew, John, about the wondrous workings of "The Jellybean Jar and Reaganomics":

" . . . You see, these jellybeans belong to the government and for years people have been eating more jellybeans than they put back in the jar. We have a deficit in jellybeans. Now what President Reagan hopes to do by 1984 is have as many jellybeans in the jar as we consume."

"How is he going to do that?"

"By cutting down on the people who can have jellybeans. The fewer people who get jellybeans the less chance there will be of the jar getting empty."

"That makes sense," John said.

"Now I'm going to give you 10 jellybeans."

"What for?"

"It's a tax cut which you're entitled to under the Kemp-Roth Jellybean Bill . . . . "

Forget the mutterings from Wall Street. Ignore the gathering of the press pack in Washington. Those are the kinds of words that signal the real end of the Reagan Revolution's honeymoon. Now, you can be sure, the pundits will soon follow suit. And if they arrive at a new consensus, can the political opposition, even if they are the divided Democrats, be far behind?

Artie and Russ, you never knew the power you possess.

For the Democrats, even more than usual, these are uncertain times. The political routs of spring and summer, with their attendant humiliations, for individuals and for party, appear happily behind them. Those earlier forecasts about their imminent demise, repeated so often, have proven premature. They have survived their defeats and nourish glimmerings of hope that better days lie ahead. Somehow they have stumbled into what looks to be an autumn of opportunity. Yet they continue to thrash about with no clear direction, and no clear alternative to offer. They remain a political party in search of a purpose.

Privately, they talk about tactics and strategy to be employed in campaigns to come. They debate whether it's time to say the emperor has no clothes, but cannot agree on the method or device to make the charge most effectively. They anguish over the price of remaining silent, or seeming to be so, or whether to discipline defectors in their ranks, but find no easy answer to their dilemma.

Part of their problem is real enough. The power of the president to command attention remains as great as ever; probably, in Ronald Reagan's case, it's even greater. Those who speak out speak strongly and consistently, among them Sens. Gary Hart of Colorado, Ernest F. Hollings of South Carolina, Daniel Patrick Moynihan of New York and Rep. Morris K. Udall of Arizona, find their words largely ignored in the national press. Their various legislative proposals (such as Hart's recent bill to delay the effective date of the new three-year personal tax cuts until the federal budget is balanced) often go unreported.

Besides, they know too painfully well how effectively this popular president has been able to work his will so far in Washington. And no matter how vulnerable he now seems, or how dubious his critical economic policy, they still harbor doubts about the outcome and uncertainty about what the people really want and are willing to support.

So out of their debates emerges a choice: caution over confrontation. Like the lyrics of the September Song, they have decided to play the waiting game. A peril exists in such a strategy. The song warns about it, for the days for action and creativity do dwindle down to a precious few, in life as in politics.

But they wait: wait for Reagan to falter, wait for his program to unravel, wait for the truth about its inherent contradictions to seep out, somehow, into the country, wait for their public vindication at the polls.

Even if they won't help themselves, they can look for something else to help them. They can always wait for another salvo from Baker and Buchwald to make their case, unless, of course, by so waiting they find those superb talents turned on them.