Ollie North will leave many legacies. Most enduring may be his single-handed transformation of the institution of the congressional investigating committee. His achievement was on display on his last day of testimony, during which he delivered almost none. Instead, he was made to sit in silence and marvel at the fruits of his labor as one congressman after another rose to "do an Ollie": deliver himself of a patriotic address of precisely the kind North had used to mesmerize the country for a week. In content, most of the speeches were critical of North. In form, they paid him the ultimate homage of imitation.

The conceit of the Iran-contra committee is that it is simply an investigative body. As Rep. Lee Hamilton put it in his rhapsodically received closing lecture to North, "{I}t is not the task of these committees to judge you. As others have said, we're here to learn what went wrong, what caused the mistakes and what we can do to correct them." Just the facts, ma'am.

This is pure pretense. If the real purpose of these investigative committees is to find out what happened, establish a record and offer recommendations, that could be done -- it has been done by countless commissions of inquiry -- by meeting privately and then making all the testimony and recommendations public. But this approach offers no drama, no show, no opportunity for political advantage. Hence the media-saturated hearings. They are not about facts. They are designed to advance the interests of one political party or one branch of government against another. Nothing wrong with that. The struggle for power is the essence of politics. The only thing wrong is the Sergeant Friday pose and the contention that a show trial is really a fact-finding mission.

Ollie's genius (or perhaps his lawyer's: we await the book) was to grasp the real purpose of the hearing and to make it all show and no trial. Since it was a show, he would win by making it his kind of show, rather than the committee's. Instead of an inquisition, he turned it into a patriotic parade, a rhetorical pageant. He handled every difficult question by deftly slipping into a soliloquy at once hokey, stirring and (as Tom Shales put it perfectly) vaguely deplorable. At the first sign of trouble, he would pull an Ollie: embrace his kin, run up the flag and salute smartly.

By the weekend, the committee was stunned. By Monday, it had found a strategy: let Ollie act as media lure, then ignore him and speak to his audience. How? Precisely as he did, under fluttering flags.

First, there were the memories, all-American childhoods recollected in tranquillity. "Colonel, when I was a young boy, growing up in Ohio . . ." began Rep. Michael DeWine. Sen. George Mitchell recalled his parents ("my father, the orphaned son of immigrants"), then waxed nostalgic about how moved he was when, as a judge, he swore in new Americans. Rep. Louis Stokes recalled his widowed mother, who raised him and his brother. She would be so proud to see him today. "Only in America, Col. North, only in America."

Then, the righteous indignation of Sen. Warren Rudman, once again sailing against the wind, who courageously came out against "ugly ethnic slurs against our chairman." His anger was visible, as it should be on TV.

And finally, the closing homily, delivered by our chairman, Sen. Daniel Inouye, to a stone-faced North. It began with the story of George Washington and the cherry tree. It crested with a firm endorsement of the Constitution: "I've always felt that, as long as we daily reaffirm our belief in and support of our Constitution and the great principles of freedom that were long ago enunciated by our Founding Fathers, we'll continue to prevail and flourish."

Ollie could not have said it better. He had conquered. They had become like him.

Political institutions change their nature imperceptibly. Those who are the first to understand the nature of the change win the game. The party convention, for example, began as a means of selecting presidential candidates. The primary system and television then transformed it into a stage production for showing off party and candidate. In 1972, Richard Nixon understood this and had his nominating convention thoroughly choreographed. George McGovern did not and found himself delivering his acceptance speech at 3 a.m. to a few insomniacs. Every convention since has made Nixon's a model.

The congressional investigative committee began as way to probe scandal. Oliver North, pioneer, understood that it, like the party convention or the political rally, could be turned into a backdrop. Interrogation could be turned into a cue for patriotic sound and light, no slides necessary. North redefined the role of witness.

And of inquisitor. After four days of North, committee members were complaining loudly. The chairmen had gotten it all wrong: they had turned the hearings over to the lawyers. What is wrong with lawyers? Isn't their job to inquire into the facts, ma'am? Exactly. That is all they are permitted to do. Mr. Nields and Mr. Liman could not conjure up a widowed parent or fallen comrade. Against a lieutenant colonel armed with an 11-year-old daughter, they were defenseless. The committee members demanded that things be turned over to them. Only they have the professional training. Only they could do an Ollie.

And so they can.