"You know how stockbrokers have certain stocks that they watch more closely than others," said Richard B. Wirthlin, President Reagan's pollster. "Well, this is the question that I watch. It is a basic question: Do you think the country is headed in the right direction or do you think we are on the wrong track?" Many pollsters use their own variants of the same question, but Wirthlin's reading is the most interesting at the moment because his client is the president of the United States.

You look at the solid and dotted lines charting the right direction-wrong track answers at intervals of a month or less and you see the history of the past year and the shape of this political moment, clearly sketched, as it is in the mind of Ronald Reagan.

Last January, on the eve of Reagan's inaugural, the rating was minus 34; that is, 34 percent more people thought we were headed down the wrong track than in the right direction. With the economy in the doldrums and the hostages still stuck in Iran, that was not surprising.

Through the spring, as the Reagan presidency began and his program took shape, the negative and positive lines began to close. There was an upward jump, a sigh of relief, in the first poll after people knew Reagan was recovering from his gunshot wounds, then a resumption of the steady upbeat trend.

By summer, the mood of the country was almost euphoric. Wirthlin logs in major events on the time axis of his chart and there are four he noted in the short span from July 7 to Aug. 20: the nomination of Justice Sandra Day O'Connor to the Supreme Court; the presidential TV appeal for support of the tax cut and quick congressional approval of that bill; Reagan's televised response to the air traffic controllers' strike, warning that he would fire those who stayed out more than 48 hours; and, finally, the downing of two Libyan jets by Navy fighter aircraft.

In political terms, every one of those actions was a winner. Taken together they boosted the right direction-wrong track score to a positive 20. Hope was beginning to triumph over fear.

Alas, not for long. Interest rates peaked in September as Reagan told the country there would have to be more budget cuts. The defense program was announced. Anwar Sadat was murdered. The AWACS plane sale squeaked through the Senate. The Stockman interview appeared. The president put his nuclear arms control proposal on television and vetoed his first bill in order to force further spending cuts from Congress. National security adviser Richard Allen stepped aside under investigation. The recession deepened. And martial law was imposed on Poland.

The two lines jiggled a bit, but the trend was as unmistakable as it was discouraging. In early December, the lines crossed again, headed the wrong way, and in the latest, mid-December reading, the scorecard showed minus 8, a far cry from the deep gloom of last January, but equally far from the euphoria of July.

Looking at those lines on the chart Wirthlin spread on his conference table last week was like looking at the cardiogram of the nation. Captured on those lines are so many human decisions and emotions: the ebb and flow of optimism and discouragement, of jobs found or lost, of education started or deferred, of purchases made or delayed, of plans conceived or abandoned, of dreams fulfilled or crushed.

Two lines on a piece of paper, scrutinized by a president wondering in personal terms, "How'm I doing?" and in political terms, "How long can I keep the Congress with me, the people in my camp?"

Leadership is such a mysterious process, so dependent on inner impulses and intuitions. Does it help or hinder a leader to have that chart put before him every month, with the events of the last 30 days correlated to the fluctuations in the public's morale?

I don't know. Most of us have our hands full dealing with our personal moods, let alone the public mood. Perhaps it was easier in a less sophisticated age, when survey research did not supply such an instant measurement of reactions to events.

But we live in our own time, and Ronald Reagan, whose success in two separate careers has depended on audience reactions, is probably better equipped to deal with the pressures implicit in that graph than most presidents.

Surely he knows, as he returns to Washington for his second year in the job, that the verdict of the people is hanging in the balance, tipping in the wrong direction but not irretrievably so. Not yet, anyhow.