So Pat Roberts was the president and was facing an agricultural disaster, a bioterrorism attack that had quickly spread disease to millions of U.S. farm animals. And he knew the decisions he would make would come to define his administration — imaginary though it was.

Lawmakers such as Roberts are often tapped to play the president in organized drills and “war games.” The Kansas Republican’s opportunity to play the role of commander in chief — a job he’s not known to covet in real life — came in 2002, near the end of his first term in the Senate, when the Agriculture Department staged a multiagency counterterrorism exercise called Crimson Sky.

Although the scenarios were concocted, they were so vivid that Roberts often described them at congressional hearings years later — especially his order to the National Guard to destroy tens of millions of affected animals. “We ran out of ammunition,” he remembers.

The grim details of Crimson Sky have come to mind during the first wave of 2008 presidential debates, in which 10 Republicans and eight Democrats have tried to lay out their qualifications for the job. But the questions they have faced and the short, practiced answers they have given hardly seem up to the unforeseen challenges that one of them will probably confront during a term that ends in January 2013.

Perhaps what the voters need instead of more debates is a series of war games — hypothetical exercises like those that are regularly employed by military commanders and other government leaders to gauge decision-making skills and processes.

Imagine sending each presidential aspirant into a mock situation room with a half-dozen advisers of her or his choosing. Inside, this virtual Cabinet could be confronted with a complex scenario, and the deliberations and decisions could be captured on camera for the voters to analyze. Talk about reality TV. It would be better than “24” or “The West Wing” — though the stakes would be much more real.

That a campaign media consultant would permit a client to participate in such an unscripted venture is unlikely. But some other brave public officials have already done just that. Earlier this year, Julie L. Gerberding, director of the Centers for Disease Control and Prevention, allowed four reporters to observe the first of a series of drills to test how she and her senior staff would respond to a simulated pandemic flu outbreak. Gerberding even participated in a mock news conference, with CDC officials playing the parts of reporters as the real journalists watched.

There’s also precedent for the press to stage its own role-playing opportunities. During the 2004 campaign, the Atlantic Monthly organized a military planning exercise “as a preview of the problems Iran will pose for the next American president.” The three-hour meeting involved former officials and academics talking through U.S. military options for responding to a hypothetical Iranian nuclear threat. The bipartisan group’s discussions, published in the magazine a month after the election, included detailed analysis of the complications posed by possible unilateral intervention by Israel, the difficulty in targeting dispersed and clandestine targets and the spill-over effects of any hostilities on U.S. troops still in neighboring Iraq. The conclusion: There were no good military options in Iran.

The Atlantic’s exercise was quite a contrast to the sound-biting on the same subject during this spring’s presidential debates, in which top candidates from both parties refused to take tactical nuclear weapons or any other military options off the table when it came to Iran — but revealed little about how they would sort through their options.

“President” Roberts had no such easy out in Crimson Sky. He and his mock Cabinet were informed that terrorists had attacked the U.S. food supply by spreading foot-and-mouth disease — a highly contagious virus that infects cattle, pigs and other cloven-hoofed animals — and that the disease had appeared in much of the country. Humans would not be directly at risk in such a scenario. But, with American agriculture exports stopped, the movement of livestock restricted and panic setting in at grocery stores, the president soon decided that the National Guard should begin shooting the animals to control the outbreak.

The theoretical impact would stick with the senator for years to come as he grilled administration officials about their actual bio-defense plans. “We had to dig a ditch in Kansas 29 miles long, the size of a football field wide so [disease] wouldn’t leach into the groundwater,” he said at one Senate hearing, recalling the disposal process his advisers settled on during the exercise.

Hoping a top-tier presidential contender would participate in such an exercise may be hoping for more than the current campaign can deliver. But many presidencies have been shaped, if not defined, by events not fully comprehensible at election time — George W. Bush and Sept. 11 being but the most recent example. Assessing which candidates are best suited to respond to new, complex and fast-paced challenges will probably require much more than has been revealed in the debates so far, both from the candidates and from those whose job it is to question them.

Mark Stencel is deputy publisher and a technology columnist for Governing magazine, published by Congressional Quarterly Inc.

First posted June 22, 2007 1:40 p.m.