FRESNO, CALIF. -- Virtually the first question a visitor from Washington was asked at the midweek luncheon here of the San Joaquin Valley Town Hall was this: Will the stock market crash shock the politicians into doing something, finally, about the ever-mounting national debt?

The answer from this corner was a resounding ''Maybe,'' but the impulse was to rush over and hug the blue-haired lady who had asked. She had just confirmed this itinerant reporter's belief that the people are way ahead of the politicians on this issue.

Let me stipulate at once that I do not know what caused the 22 percent drop in the Dow Jones average last Monday -- whether it was computerized trading programs run amok, panic in the brokerage offices or a reaction to real-world economic, political and diplomatic concerns.

What I do know is that the people of this country have seen this trouble coming for a year or more and are impatient with the big shots' obtuseness in getting the message.

Last autumn, when three colleagues at The Post and I fanned out from St. Louis to do a week of voter interviewing in various parts of the country, we found the mood dramatically altered from what it had been at a similar point in 1984.

The 1984 Olympic year euphoria, fueled by the psychological liberation from the nightmare of inflation, had made people welcome President Reagan's celebratory ''morning in America'' campaign commercials. Back then, there was an irresistible impulse to savor the moment, to let the good times roll and to reject any dissonant signals of trouble ahead.

Last fall it was very different. Inflation was still low (for which Reagan and the Republicans were thanked), but disquieting signs of economic upheaval were noted in many of the living-room interviews. Companies were closing and jobs were being lost through mergers and acquisitions, shifts to overseas sites or foreign competition. The voters we met were spontaneously linking the worsening of America's competitive position in the world, the wastrel red-ink budgetary practices of the Washington politicians and the wheeling and dealing of the Wall Street takeover artists as symptoms of a national disease: economic excess.

What we reported at that time was an increasing disquiet, a sense that we were living beyond our means, a fear that there would be a day of reckoning.

These informal interview findings were supported by the results of our national survey, using the favorite question of Reagan's pollster, Richard B. Wirthlin: Is the United States basically on the right track or seriously off on the wrong path?

For the first time since the recession of 1981-82 ended, the answer to that question became primarily negative in 1986. Exit polls after the November midterm election showed the sharp decline in national economic confidence was probably the single greatest factor in swinging the Senate majority to the Democrats.

When we went out again last spring to Knoxville and again in the summer to Cleveland and the Chicago suburbs, we heard the same thing. Times were good for most people, but trouble lay ahead. The polls continued to confirm those findings. In September The Washington Post-ABC News survey found respondents saying by a 5-to-4 margin that the nation was ''seriously off on the wrong track.''

The sound of the Dow Jones average cracking under the feet of the Wall Street speculators confirmed the popular wisdom. The American people knew in their guts that you cannot live beyond your means indefinitely without facing the music. A country that pays 80-some cents in taxes for every dollar's worth of defense and domestic services it receives from the government; a country that borrows more each year from foreigners to finance its national debt; a country that buys more from abroad than it is able to sell -- that country is looking for trouble.

Until very recently, the voters' fears centered on their children. The apprehension was that they would pay, one way or another, for our wastrel habits.

When the Dow Jones cracked, you could feel the shivering sensation that the day of reckoning might be at hand. That's why so many of the comments and questions heard here centered on what those Washington politicians were prepared to do.

The only answer I could give was: wait and see. The Senate, under its old Republican and current Democratic majorities, has voted repeatedly to discipline spending (domestic and defense) and raise revenues. The House blew hot and cold on the issue under Tip O'Neill, but has matched the Senate in self-disciplined budgeting this year under Jim Wright and Bill Gray. Reagan has been the reluctant dragon, balking at talk of tax hikes and defense cuts, but he sounded at times this past week as if he was finally ready to listen and negotiate.

Years back, Sen. Alan Simpson (R-Wyo.) explained what it would take for the politicians to make the hard budget choices and step up to the challenge the voters clearly see. ''We all have to link arms and go over the cliff together,'' he said.

Last week, it felt for a time as if we had fallen off that cliff. That may be enough to get the politicians to link arms.