IOWA CITY -- Here's a question for the presidential candidates. I've been asking it for 15 years, and have yet to get an answer.

In 1972, while I was an FCC commissioner, I was asked to do television interviews with most of that year's presidential candidates. It was frustrating, because the candidates had long before worked out most of their pat answers to standard questions.

The notion of giving them an unexpected experience, like throwing a softball to see whether they could catch it, or tipping over their chair to see how they'd respond, was tempting, but not seriously pursued. What I settled on instead was the process question.

It goes like this. "Assume, senator, that everyone here agrees you are 'right on the issues,' whatever that may mean to them. And assume you are elected president. How will you accomplish your objectives? Will the Washington sub-governments have less power than they do now? Why? Will children and the poor have more power? Why? Will the broadcasters have less control over the Maritime Administration, the military-industrial complex less control over defense appropriations?"

These are the questions I have continued to put since 1972. (Iowans feel entitled to, even responsible for, questioning presidential aspirants.) But in all those years, there have been few who even understood the question (Hubert Humphrey was one). None has had an answer. ("I'll appoint good people to office" is the most one can hope for -- a revealing bit of evidence of their failure to understand the problem.) This year's crop has, so far, done no better.

Emphasizing process does not detract from the importance of "the issues." There are differences between candidates (in past actions as well as campaign statements) regarding such things as nuclear disarmament, jobs, health care and education -- though the positions may reflect the advice of pollsters and political advisers more than well-considered political philosophy.

But even if a candidate's positions on the issues are long and deeply held, they may very well undergo radical revision when confronted by political realities. As President Truman observed: "When it comes to these bureaucracies, I can't make them do a damn thing." As anyone who has worked in Washington knows well, the primary problem with the intentions of platforms and position papers is the enormous gulf between public interest and political process.

Let's ask the candidates the following questions: Have they read Richard Neustadt's "Presidential Power" and comparable studies of process? What did they learn? How do they propose to build the coalitions and political support necessary to accomplish those things in "the public interest" that are of low priority for the mass media and public but of high priority to the special interests that oppose them? How will they break the grip of the sub-governments: that fusion of each individual industry's oligopolistic corporations, trade associations, congressional subcommittees, trade press, PACs, specialized lawyers, eating clubs, lobbyists, publicists and government agency personnel that seems to run Washington?

But why stop here? There are other similar questions to be asked. Is the candidate interested in the management of the federal government at all? What management experience, theories, preferences -- or "style" -- will he or she bring? How will the candidate collect, evaluate and select nominees for presidential appointments -- or proposals for legislation? How will he or she apportion functions and staff between Cabinet departments and the White House?

The potential process questions are endless. But at this point few if any such questions are ever put to the candidates. They should be. Because the qualities it takes to govern are different from the qualities it takes to be elected. And after the sparring over "the issues" and personal lives finally ends, and the ballots are counted, it is the process of the presidency that will make the difference in our lives. Nicholas Johnson, a former member of the Federal Communications Commission, is a writer and lecturer.