AMERICA HAS become a nation of crisis aficionados, accepting crisis -- esspecially a crisis involving the president -- as the medium by which character and status are most surely revealed. This builds a certain skew into the nation's political life, since the traits and rankings that emerge at a time of crisis do not necessarily have much to do with good governance, which is unavoidably heavy on organization,; expertise and routine. The sequence that began when President Reagan was shot did, nonetheless, fling open a window through which the country will be peering for some time for clues.

We were struck first of all by the courage and agility of the president's guard. Questions must be asked about how the attack came to be made, but, even as the bullets were being fired, a number of men put their lives on the line. It was an impressive showing of duty and instinct alike.

With concern for the president running high, Dr. Dennis O'Leary then became the nation's chief handholder. This is not to minimize his role in putting into smooth effect his hospital's disaster plan. But his calm, comprehensive and good-natured briefing of the press was just what a doctor would have ordered to deal with the mounting anxieties of Americans and others.

The main ring, to be sure, was occupied, and held, by Mr. Reagan's White House and Cabinet aides. The important thing is that from the standpoint of the national interest, apparently everything went well. The country was covered against panics and emergencies during the mercifully few hours of early uncertainty. Thanks in good measure to Mr. Reagan's remarkable recuperative powers -- not to speak of his one-liners -- his government shifted promptly into a mode of operation for which "business as usual," the White House term, is an exaggerated but acceptable designation.

That said, it must be asked whether Secretary of State Haig committed a breach of taste or protocol Monday afternoon in the course, or in the name, of steadying the ship of state. Presumably, he meant to be plugging the hole left by the hospitalization of the president and by the temporary absence from Washington, and from the White House situation room, of Vice President Bush. Perhaps his performance would have passed with little notice if he had not; been at the center of the previous week's flap over White House "crisis management." In any event, his agitated TV manner and some of his words, including his claim to be "constitutionally" third in line for "the helm" and his assertion that "I am in control," did sharpen the very questions of personal style that had arisen the previous week. Nor was it comforting to learn later that the secretary of defense had found it necessary to ask if Mr. Haig had edged into his place in the military chain of command.

Mr. Bush, meanwhile, was winning appreciative nods for acting in the modest and dutiful spirit that has come to be expected of vice presidents at moments of presidential accident or illness.

The media: Television made the public a stupefied witness, dozens of times, to the crime. Television also made the public a witness to all the excitements and false starts, and quick fixes, of its own news-gathering process. You could almost see the journalists on the screen hunching their shoulders at the accusations likely to come, the inevitable critique of their role by people who would have the leisure to weigh choices they had had to make on the spot. We of the writing press, whose job came down to putting the pieces together for the next morning, watched for hours.

In sum, crisis may be a flawed medium for exploring either government or society. But this one provided Americans with a degree of reassurance to offset the shock and the injury caused by the gunman. The reassurance lies in the sense of sharing not only vulnerability but also the capacity, personal and institutional, to deal with a terrible event.