It is August in Washington, the August of a brutal and unforgiving summer. Congress is in recess, much of the government is on vacation and a good many journalists are taking the sun at the beach. Maybe that explains why President Reagan's long-awaited speech on the Iran-contra affair passed through town like a boat that leaves no wake. There is, though, another explanation. Whatever the season in Washington, it's autumn for Ronald Reagan.

On its face, the president's speech was a preposterous explanation. He explained almost nothing. Did he agree with Adm. John Poindexter that he would have approved the diversion if told about it? Did he think CIA Director William Casey knew about the contra diversion and, if so, did the president think Casey should have informed him? Had he actually approved a plan to ask Kuwait to free the terrorists it is holding in exchange for Americans being held in Lebanon? Did he really tell White House aides that Iran was losing its war with Iraq and therefore needed American arms? And, if so, how does that square with his public pronouncement that the arms were insignificant and could not affect the outcome of the war?

None of these questions was answered in the president's brief speech. The White House says that's because the American people are bored with the scandal. It's over "as far as the audience is concerned," Reagan told Time magazine. But what really seems to be over is the Reagan Era. That same Time interview finds the president looking fit and characteristically upbeat: "The Great Houdini of American politics." Maybe. But lately Reagan has pulled nothing but skunks out of his hat.

In his forthcoming book, "Man of The House," a critical Thomas P. (Tip) O'Neill, the former speaker of the House, has some harsh things to say about Reagan. But he is also admiring of the way Reagan and his staff were single-minded in pursuit of their legislative goals. That Reagan and that staff now seem to be a thing of the past. One of Reagan's stated goals is a balanced-budget amendment. There is little chance of that happening. Another goal has been to democratize Nicaragua by ousting the Sandinista regime. Now there is little chance of that happening either.

In fact, the president's Central America policy is in disarray. First he joined with House Speaker Jim Wright to come up with a diplomatic initiative and then saw it brushed aside by one proposed by the Central American presidents. The president then tepidly endorsed that one, to the understandable dismay of conservatives. For years, they had heard Reagan say he would make the Sandinistas cry uncle. Now the cry seemed to be coming from him. His policy, both overt and covert, has always been animated by anticommunist zeal, by a certainty regarding the nature and the intentions of Marxists such as the Sandinistas. Now the energy seems to be gone.

In both domestic and foreign policy, Reagan has collided with reality. The smug Sandinistas, as well as the Democrats in Congress, seem to understand that. The nation is unenthusiastic about funding a war in Central America, and that muddled sentiment is reflected in Congress. The votes for continued military aid to the contras may not be there. Similarly, Reagan talks about a balanced-budget amendment, but once again this is more a wish than a program. Once again, the votes are not there.

Like generals, politicians and the press fight the last war. The Iran-contra hearings were supposed to be this decade's Watergate. They weren't because they couldn't be -- because a foreign-policy scandal lacks the menace and simplicity of a domestic one. But in their own way, the Iran-contra hearings were instructive. Maybe the American people learned no lessons about separation of powers and other esoteric issues, but they did learn something about Ronald Reagan. His contradictions, admitted lapses in memory and inability to control his personal staff give off the whiff of genial incompetence. In his speech, the president said, "I am the one ultimately accountable to the American people"; but that's not the way we see it. Increasingly, he is viewed as marginal.

The easy days of governing are over for Reagan. The hot summer of 1987 has taken a toll on him. His simple, endearing policies got twisted by a convoluted world. He bargained with terrorists for the lives of Americans; his subordinates funded a war by stealing from the cookie jar. His fellow conservatives are unhappy and restless about his confusing plans for the contras. Congress is controlled by Democrats, and the people, still affectionate toward this decent man, increasingly find him irrelevant. It's August in Washington, but it's autumn for Ronald Reagan.