In one of his famous adventures, Sherlock Holmes solved the mystery at hand by paying attention to the obvious. So obvious was the solution, in fact, that no one other than the great detective realized its significance.

It was the dog that didn't bark that provided the answer to the riddle.

This fall election, now just eight days away, is becoming something like Mr. Holmes' famous canine. It's what has not happened, more than what has, that holds the key to the public verdict about to be rendered.

Consider the situation. Here is the country, demonstrably in its weakest economic condition in decades, with real suffering being experienced for the first time by millions of Americans entering the ranks of the new poor. Yet no massive political protest appears to be forming.

Consider also that two years after his presidential election, Ronald Reagan has alienated just about every significant bloc of voters necessary to form an American political majority.

Women are clearly unhappy with him and his policies. Their reaction has been uniform wherever I have visited in the past few weeks of traveling across the country. Blacks feel even more negative about his presidency. They express greater hostility, even hatred, toward him personally than I can recall coming from any other group toward a president in the past 20 years.

Blue-collar workers, so many of whom voted for him in 1980, have turned against him. They view him as a rich man's president unconcerned with ordinary people.

Jews, who backed him in greater numbers than had been the earlier pattern of support for Republican presidential candidates, are critical of his policies toward Israel. Roman Catholics, who are hearing more from their priests these days about the old concepts of social justice and their application to events today, also appear more ambivalent about him.

Even those who remain solidly for him, mainly more affluent whites, business executives and other professionals, widely agree that his views on defense spending are out of line. They want to see a better balance struck between domestic and military spending and often express concern that he seems extreme and too inflexible.

These are all, to be sure, generalizations, but they are based on conversations with people in all corners of the country.

Yet, there are no signs of protest. Why?

Again, some generalizations:

* This midterm congressional election period does not provide a true test of Reagan's popularity. He is not on any ballot and faces no clear opponent. No matter how votes are counted Nov. 2, he will remain president. People do not see their votes as affecting him directly.

The political reality is otherwise: how those votes are cast will affect the way he is able to govern. But that is not well understood or discussed. These facts add up to one conclusion. Although Democrats are trying to make this election a referendum on Reaganomics, they cannot really make it one on Reagan personally.

* Personal conditions come before political considerations. Many of the people most directly affected by the recession are too preoccupied with their own problems to pay much attention to local and statewide races.

They are dealing with unpaid bills, unfound jobs and the unaccustomed painful experience of applying for benefits payments. Many of the newly unemployed, particularly union members whose factories are shut down, are leaving their areas seeking work elsewhere. Thus, they will be less likely than normal to vote.

At this point, fear and frustration are the emotions most encountered among their ranks. Anger, always the last ingredient of protest to form politically, has not yet risen nationally in substantial measure.

* However disappointed or disenchanted people may be with Reagan, nowhere is there a strong belief that he is responsible for all of the problems. People do not buy his repeated assurances that all is well and that their lives are better since he occupied the White House. They know personally that is not true. Nor do they agree with his blanket assertions of blame.

All of the old Democrats and all of the past presidents of whichever party aren't responsible for all of our problems, and everyone knows it. But people also know that there is more than enough blame to go around and that economic troubles didn't start with Ronald Reagan's inauguration.

Furthermore, it's interesting how often people, whether in labor or management, will accept responsibility for contributing to the nation's woes by being less productive or too selfish over the years. So, too, they will say, was the entire country.

* A more intense feeling of protectiveness on the part of the public surrounds this president. This is the most complicated emotion of all, involving not just how people feel about Reagan personally, or his policies or even his performance. It involves how they feel about the presidency as a symbol of American stability and hope.

People want to believe the president has the answers. They want him to succeed. That has always been the case, but it is especially so now. Too many failed presidents have passed before the public in recent years, and the country desperately needs a winner.

In this connection, I have been struck with how many people this fall have volunteered the example of Jimmy Carter. However critical they are of Reagan, they are even more so of Carter. The Carter promises are remembered and are equated with his failures.

Today, with so much doubt and hardship everywhere, the country desperately wants a winner. For now, Reagan appears to be the beneficiary of that wish. That feeling could well minimize what, by all political logic, should be a disaster for his party this fall. But it also bears some longtime political peril for Reagan and for Republicans.

The period after the election promises to be fateful politically and economically for the country. Unless there is a substantial and relatively fast improvement, the present numbness, fear and frustration could turn dramatically into something more volatile.

For Reagan, the great test will come then. Memories of the present difficulties will not dissipate easily. Groups already alienated are sure to become more so. The danger is that anger finally will be felt, with what consequences nationally no one can say.

As Sherlock would have said, when searching for the obvious clues, beware when the dog starts to bark.