WITH THE PRESIDENT and Congress back

in town, and the long vacation ended, politics gets serious again. Mr. Reagan's central concern continues to be the state of the economy. It's time for him to bring order to his program by sorting out his priorities, acknowledging that his various goals of last spring are inconsistent with each other, and give the country some clear idea what comes first.

Otherwise, his program is going to be nibbled to death in the endless quarrel over budget arithmetic and the forecasts of deficits. The computations are arcane, and not everyone finds them terribly interesting. But they have enormous force because they are a manifestation of the deeper confusions generated by the president himself when, in his engagingly nonchalant manner, he keeps holding out promises that do not fit together. The deficit debate has become a surrogate for the larger doubts about the administration's intentions.

Mr. Reagan keeps talking, for example, about the need for "economic recovery." Recovery from exactly what? The term usually indicates reflation to end a recession. But if the country's in a recession now, it's a very shallow one that was imposed, as a matter of deliberate policy, by the Federal Reserve Board with the explicit support of the administration, to curb the inflation. Does the talk about recovery signal, as in the past, presidential intervention to make the economy grow faster and generate more jobs? If that's it, what happened to the campaign against inflation?

And let's not keep responding that the administration has discovered an exciting new theory, understood by it alone, that will produce faster growth, lower inflation and 6 percent mortgages by the next congressional election at the latest. It's that kind of talk that's frightening business people and investors. But Mr. Reagan keeps saying amiably that, if only Congress keeps cutting the budget, the path will soon lead the country from the present "soggy" economy to higher and firmer ground, with a better view.

Is it really a soggy economy? The rate of business expansion this year will be low--but isn't that the reason for the welcome decline in the inflation rate? Except for automobiles and housing, most of the economy is holding up pretty well. And isn't it also time for the administration to start discussing the painful truth that its policy implies lower production rates for cars and houses than those to which the country has recently become accustomed? The administration takes great pride in having turned Americans, in some degree, away from consumption and toward saving and investment. Monetary restraint means buying less on credit. Doesn't that mean fewer new cars and new houses every year?

Mr. Reagan celebrated Labor Day by going to New York and presenting the mayor with a check to begin work on a huge highway reconstruction project. That's classic reflationary, public works politics. It's what you do if you want to create jobs, and perhaps win friends among the construction trade unions at the same time. Mr. Reagan pledged himself to a rise in employment over the next five years almost as rapid as that in Mr. Carter's presidency. But his audience was full of people who remember how Mr. Carter achieved that acceleration of employment, and what it did to the inflation rate.

Whether the federal deficit is a few billion higher or lower next year is not going to be crucial to the fate of the republic. The controversy over the deficit numbers is now threatening stable economic expansion because it is the focus of the fears that Mr. Reagan hasn't yet, in his own mind, made the hard choices--and that perhaps he isn't going to make them.