Quirky questions combine with evasive answers to blur issues and obscure positions. Cameras cause candidates to pose. So disparagement of debates among presidential candidates comes easy.

But the Republican forum held by the Des Moines Register the other day proves anew what the debates did in the 1976 presidential campaign. Imperfect as they may be, these encounters provide ordinary citizens the best available access to candidates. From the session here, discerning voters could extract a comprehensive rundown on all the Republican candidates for president.

Bob Dole, the senator from Kansas, distinguished himself as a sharp wit, fast enough on his feet to qualify as a successor to Johnny Carson. But Dole wasn't just kidding when he said that his position on the podium between John Connally and George Bush placed him "between two of the richest men in America." Nor when he added that he was "proud to be with such class." Behind the wisecracks, as behind much of what Dole does, smoulders furious resentment.

John Anderson, the congressman from Rockford, Ill., showed his remarkable capacity to talk straight on the issues. "With mirrors," he rightly responded when asked how it would be possible to combine a tax cut with increased defense expenditures and a balanced budget. Still, he seemed to support President Carter's embargo on grain sales to Russia chiefly as proof that he had the courage of the hardline convictions of the other candidates. He thus expressed some of the self-righteousness that has made him such an outsider among Republicans.

Phil Crane, the conservative congressman from the Chicago suburbs, came across as well-spoken and clean-cut. He picked up strong when somebody mentioned Alexis de Tocqueville and went into elaborate detail on the views of the great French political theorist. In the process he advertised a disposition to take ideas more seriously than people -- the cloven hoof of the true doctrinaire.

John Connally breathed life into what started as a heavy affair by the response he gave to an inquiry about the difference between his views and those of Ronald Reagan. "I really don't know how he stands on the issues," the former governor of Texas said of the former governor of California. "I wish he were here. Oh, how I wish he were here." Even though Connally was only kidding, there shone through the joke his impulse to get hold of some jugular and squeeze and squeeze and squeeze.

Howard Baker, the senator from Tenessee who is minority leader, asserted the quintessential Republican position on the key issues. Iran and Afghanistan struck him as "symptoms" of a foreign policy that projected "weakness." He drove home the weighty point as easily as sipping mountain dew -- a sign of an inner security, a contentment in life, that suggests one of the best-placed Republicans in the race may lack the restless appetite usually required to go all the way.

George Bush -- the former Texas congressman, CIA director and ambassador to China and the United Nations -- came up with probably the best one-line criticism of the grain embargo: Yogi Berra's classic remark, "the wrong mistake." But he stepped on the joke, and later he fluffed the first part of a question that coupled the subject of morality in politics with the issue of gays and pornography. Not only that, but Bush asked to be reminded what the second part of the question was. He thus showed a little of the nervousness that goes with doing well and, at the same time, the extraordinary gameness, the willingness to make any effort, that continues to make him a formidable candidate.

The front-runner was also present -- at least in spirit. Nobody who watched the Iowa debate could believe Ronald Reagan's claim that he did not participate for fear of "dividing" the party. On the contrary, the debate proved that Reagan stayed away because he might have lost luster. He comes on now like a basketball team that has to freeze the ball from the first minute of play.

Gerald Ford was another invisible presence. Baker, Bush, Connally and Dole all mentioned him favorably. Listening to them, one had the impression Ford had both licked inflation and solved the defense problem. Ford, if anybody, was "the winner."

To be sure, these impressions are highly subjective. But that is precisely the point. At a time of great political fluidity, when party labels say nothing, debates offer the voter a guide to the candidates. They are thus a kind of historical relay point -- a way station on the route from the political past when party was everything to a political future that has not yet revealed itself.