President Reagan is waging a contradictory political battle. He is staging a summer offensive for his "Economic Bill of Rights," designed to demonstrate that he remains relevant. Simultaneously, he has retreated into a defensive crouch on the Iran-contra affair, while aides anxiously await the testimony of Rear Adm. John M. Poindexter, a former national security adviser, about what Reagan knew and when he knew it.

No president has shown a keener understanding of television's impact, and it seems odd to have Reagan wandering around the countryside pretending that the televised hearings on the seminal scandal of his presidency do not exist. Perhaps he finds it a necessary pretense, since Reagan concluded well before the testimony by Marine Lt. Col. Oliver L. North, the fired national security aide, that no one "outside the Beltway" cared about the hearings.

Unable to persuade reporters that Americans are disinterested in the scandal, Reagan has taken the fallback position that he is not interested. After claiming that he eagerly awaited North's testimony, the president fled from questions about it once North took the stand. If Reagan's spokesmen can be believed, he was too busy even to turn on a television set.

This staggering lack of presidential curiosity is offered as a defense but has more the ring of an indictment. Regardless of what he knew, how could any president be "too busy" to watch a congressional hearing where an influential former aide dramatically accuses principal administration officials of breaking the law, lying to the American people and obstructing justice?

Reagan's conduct is part of a pattern that marked his decline in public approval. Surveys taken after disclosure of the Iran-contra deal found that even those willing to give Reagan the benefit of every doubt were disturbed by his lack of outrage over what had happened.

The 76-year-old president at least gives the impression of outrage when Democrats suggest that his administration should be discussed in the past tense. Last week Reagan offered a spirited, if scripted, comment: "All that lame-duck talk is for the birds."

Reagan has been trying to demonstrate his relevance ever since the Democrats won the Senate last year after his strenuous campaign to keep it in Republican hands. Reagan was forced back on his veto, which Congress has proved selectively willing to override.

Despite loss of the Senate and the constitutional handicap of being ineligible to succeed himself, Reagan has shown surprising ability to shape the political agenda. He boldly committed the administration to sending reflagged Kuwaiti ships under U.S. escort through the Persian Gulf, even though several influential members of Congress warned that this action could lead to war. Domestically, he took advantage of a stroke of luck to nominate an extremely able conservative candidate for a Supreme Court vacancy and set up the kind of confrontation he relishes.

This is lively stuff for a lame duck. It has emboldened Reagan to expect too much for his "Economic Bill of Rights," a pile of old proposals centered around a balanced-budget amendment that would radically limit congressional authority. In successive speeches, Reagan invoked Thomas Jefferson, Barry Goldwater and Harry S Truman in behalf of this plan, which has less prospect of legislative approval than a congressional pay cut.

Four years ago, when conservatives were pressing Reagan to deliver an economic message in his reelection campaign rather than maundering about how "it's morning again in America," the balanced-budget amendment might have had a chance. Now, it seems a tired idea capable only of rousing Reagan for one more political charge.

The Democrats have always underestimated Reagan, and they have not quite succeeded in making him irrelevant to the process. But if the president keeps pushing marginal economic proposals while shrinking from budget solutions and ducking the scandal unfolding before the nation on television, he may wind up doing more damage to himself that his opponents have been able to inflict. And the testimony of Poindexter lies ahead.

Reaganism of the Week: Speaking to the Kiwanis International convention here last Monday, the president said, "I remember the first time I was introduced to the Kiwanis {in 1964}, I was described as an actor and spokesman for American business. Of course, that's how a lot of people still think of me."