THE ASSAULT on administration foreign policy by the Senate's 38 Republicans cannot be ignored, coming as it does from a bloc that has the power to make the president pay a considerable political price, and perhaps even a diplomatic price, for his policies. But the most striking feature of the assault was that it reflects so faithfully the criticism that many Democrats also make - privately. Inexperienced if not inept on leadership, ambiguous toward Soviet power, erratic in negotiations, rough on allies - that is practically the Washington consensus. Bipartisanship is not dead; it has merely shifted from policy to criticism of policy. That line of criticism, moreover, has an international dimension. From Moscow to Peking to Bonn to Tokyo to Riyadh to Tel Aviv, echoes of it can be heard.

We have expressed some disappointment in the administration's performance ourselves over the last 16 months, and in a general way we are tempted to sign on to the Republican critique - even though its hardline military quotient is a bit excessive. Yet the critique is superficial. It does not adequately explain what the administration's problem is.

In fact, there are several problems. The first is that the president must act, with the diminished authority bequeathed him by his several predecessors, in a world in which relative power has been diffused to the point where the United States cannot work its will as once it did.That is no less so for the fact that Democrats tend to pass over the point when Republicans are in office, and vice versa.

A second difficulty is that there is no accepted yardstick of performance. By this stage in their presidencies, John Kennedy had had himself a Berlin crisis, lyndon Johnson a deepening involvemtn in Vietnam, Richard Nixon a White House encircled by demonstrators, and Gerald Ford the scalp, so to speak, of the Mayaguez. No comparative grounds there for the indictment of Jimmy Carter. Yet many people have in mind, we suspect, one particular yard-stick, the sense of design, of architecture, of knowing what he was doing, that Henry Kissinger conveyed widely, even to detractors. Mr. Carter's approach often seems random and casual. His lieutenants have won more or less respect for their personal qualities, but neither singly nor together have they compensated for his failure to appear to be in charge.

That is to say that the administration has a hard time getting its policy judged on its merits. It is not just that its "image" is pretty bad. Its style, too, cluters the picture. The early foot-on-the-floor emphasis on human rights was misplaced and confusing. The administration managed the considerable feat of convincing many, while it was winning on the Panama Canal, that is had 10 thumbs. It's a good bet to win on the Mideast arms package but it will pay a heavy toll; indeed, the bruises it has inflicted and received overall in its Mideast strivings have loomed larger than the boldness and right-mindedness of its policy. In Africa and SALT, where it is still in mid-passage, its approach has seemed erratic or unsure.

What that means to us is that, though the administration has its problems, catastrophe is not around the corner. There is time and room for happier or more generally accepted results. With persistence and restraint and more skillful attention to the political context, Jimmy Carter still has the chance to make a record in foreign policy that will not only serve the nation but also make the Republicans look elsewhere for a basis on which ti replace him with one of their own.