With all respect to Tom Brokaw, who acquitted himself admirably from the Kremlin to the Kennedy Center, the best question in the all-in presidential debate was asked by Alexander M. Haig Jr.

Haig threw a grenade right at the foot of GOP front-runner George Bush. He began with evident glee, "George, you've claimed to be the copilot of this administration, and we've known that on occasion you've been the pilot." Then he demanded to know where Bush was when the decision to sell arms for hostages was made. "Were you in the cockpit or on an economy ride in the back of the plane?"

Bush, his new found serenity ruffled, limped through a totally irrelevant discourse about "the best antiterror report any country has ever had."

Haig noted that Bush had not answered the question.

That was the high point of a lively and entertaining two hours that did not materially advance the action or add to the substance of the campaign. The Democrats were nice to each other, and Massachusetts Gov. Michael S. Dukakis continued to exhibit on-camera ease, although he ducked the question of taxes so insistently put forward by former Arizona governor Bruce Babbitt, who stood up to make his point.

What the meeting mostly did was to deepen the mystery of Robert J. Dole, Bush's only real rival for the nomination. The question is, what is Sen. Dole doing? Why doesn't he challenge Bush on his most exposed nerve, his involvement -- or noninvolvement -- in the Reagan administration's worst scandal?

The answer seems to be that Dole is trying to negotiate a separate peace with his party's right wing. Every time Bush looks at Dole, he must be glad that he got his groveling over with early. He abased himself in 1985. He licked the boots of Nackey Loeb, publisher of the terrible-tempered Manchester Union Leader; he threw his arms around Jerry Falwell and the evangelicals; he paid his respects to the National Rifle Association.

Now thanks to the INF treaty, which Bush supports with all the fervor he gives to any Reagan cause -- no matter how ambivalent the chief may be about this one -- he is able to come on as a moderate.

Dole, meanwhile, is deep in the rituals of courting the porcupine.

Dole was notably cool about the treaty. He didn't say whether he was for or against it. He said lamely that he has to "read it, study it." For a man who eats bills for breakfast, it was a curious evasion. And who is the audience he reaches by dodging the issue?

Eighty-five percent of the American people favor it. No more passionate constituency exists than in Iowa. It's a hotbed of peaceniks. Iowa's Democratic senator, Tom Harkin, says that the craze for peace crosses party and economic lines.

Former Nevada senator Paul Laxalt, during a recent test of the presidential waters, was startled to encounter unilateral disarmers among the cornfields.

But Dole has been persuaded that he must pass through the needle's eye of conservative Republicanism in order to get the nomination. Democrats regard him as a far more formidable foe than Bush in a general election, but he is concentrated on the primaries and feels he must do everything right, no matter what the cost to his reputation as a strong-minded leader and an acute politician. One of his earlier moves was to risk his standing with blacks, who remember him for his bravura performance on the Voting Rights Act extension of 1982, by voting to uphold the president's veto of sanctions against South Africa.

Just how far he feels he needs to go in order to appease the implacables was evident in his wishy-washy answer to Brokaw's question as to which report of the Iran-contra committees he supports.

Actually, said Dole, he likes both. The Republican report called the majority report "hysterical." And Dole's friend and powerful New Hampshire backer, Sen. Warren B. Rudman, one of three Republicans who signed it, called the minority version "pathetic." So Dole looks like a man with one foot on the dock and the other in the boat, not a graceful stance for one who would be leader of the western world.

No one reacted more swiftly or decisively to news of the secret arms-for-hostages deal. Dole called for a special session of Congress, if necessary, to begin investigations. But the right wing hates the majority report, and Dole feels it imperative to be leery.

Some Senate colleagues predict that Dole will come out in support of the INF treaty well before the Iowa caucuses can turn into a referendum on war and peace and that he will guide it, with his usual skill, to ratification.

But right now, Bush is the Republican peace candidate, and Dole is left to say he is a slow reader.