Without dwelling on names, it's fair to say that in all the coverage of Hurricane Katrina and its aftermath, some public officials managed to look preternaturally competent and poised and some seemed to be in over their heads. Anybody who watched TV for more than a few minutes couldn't help being struck by the discrepancies these people showed when it came to conveying leadership and radiating reassurance. But it's hard to be precise about just what those discrepancies were made of. Do some mayors and governors simply possess a leadership gene that allows them to burnish their reputations at times of unexpected disaster?

That can't be it. More likely, top leaders simply become stand-ins for government's performance as a whole, bringing upon themselves more credit--or more blame--than their personal conduct actually warrants.

It is true that to a great extent what matters is how they come across on camera. Ideally, they appear engaged and strong, while remaining calm. "The public needs to know someone's in charge and that that person is not overwhelmed by what's going on," says Richard Sheirer, New York City's commissioner of emergency management during 9/11. But strong doesn't mean emotional or profane. That's why the governor of Louisiana and the mayor of New Orleans didn't look very impressive in the post-Katrina saturation coverage. There's a fine line between tough and shrill, and both Kathleen Babineaux Blanco and Ray Nagin seemed to come down on the wrong side of it.

It's also pretty clear that the public treats elected officials as symbols for the performance of the larger institutions they speak for. No matter how impressive the leader may sound, his overall reputation comes to rest on whether he and his administration have prepared well for catastrophe. If not, the leader's reputation will begin to suffer remarkably quickly. An agency and its staff may do a lot of good things, but their efforts won't look coordinated to the public, and the blame will settle on the person at the top. That's why the Federal Emergency Mangement Agency looked so bad after Katrina and why its director, Michael Brown, became a lightning rod for all its failings, losing his job within a few days.

Conversely, this is probably why Rudy Giuliani became the contemporary standard-bearer, following the World Trade Center attacks, for effective leadership under pressure. Giuliani found an eloquence equal to the moment, but the main reason he is remembered so fondly--his performance erasing memories of all the controversies of his mayoral tenure--is that the city functioned the way it was supposed to.

It may not be fair that a top official ends up saddled with blame or covered with glory, depending mostly on how she comports herself on TV and how hundreds or thousands of other government workers respond to a disaster. But when you think about it, that's not too different from what happens when leaders are blamed for or credited with running the economy or solving other big problems that are, in reality, just as much out of their control as the events that follow upon a major disaster.