Leading up to the moment of cold truth just before midnight Wednesday when Ronald Reagan finally decided something was very wrong, agents of Gerald Ford were engaged in an exercise they called "segmenting" the presidency that looked much like a backdoor road to power.

What Reagan refused to accept was the ultimate in a "Fordization" of the presidency that has been well under way for several weeks with senior officials in the Ford administration joining the Reagan team. In the frantic talks Wednesday night, they were trying to institutionalize that power in a future Reagan administration.

Unanswerable questions of constitutional propriety pulled Reagan back from the brink. But the exercise demeaned the prestige of the Republican Party's two dominating figures. Reagan emerged looking disorganized and careless of the prerogatives of the office he seeks. Ford came over as relentlessly insensitive and perhaps vindictive about the man whose 1976 challenge he blames for losing him the presidency.

Two key figures in Ford's apparatus -- Henry Kissinger and economist Allen Greenspan -- asked for what was constitutionally impossible to give: operational control by Ford of "the national security portolio," the domestic budget and the White House chief of staff. Although some Ford advisers felt Reagan had accepted this package, he never quite did.

"They offered Ford the right to name the secretary of defense," one Ford insider told us, "but that wasn't enough." That it wasn't enough was perhaps less the judgement of Ford himself than of his close aide from White House days, Jack Marsh. It was Marsh, the lawyer inexorably pounding out an agreement, who talked about "segmenting" the presidency.

But even if Ford was not aware of the letter of his negotiators' demands, they would not have squeezed the Reagan agents so remorselessly without feeling encouragement and approval from the former president.

Ford, who could hardly utter a favorable word about Reagan in his well-received speech to the convention Monday night, has harbored four years of resentment about him, spiced with a general low regard. That could be not wiped out in four hours of pressure-cooker talk.

The operation culminated a process that has concerned Reagan's conservative supporters, who fear Ford Republicans want to undercut Reagan's tax-cutting and national defense policies.

Bereft of experienced political talent since the sacking of John Sears as campaign manager Feb. 26, Reagan has been taking aboard experienced and respected old Ford hands such as William Timmons and Stuart Spencer as key political operatives. There is no sign that Timmons was intimately involved in the Wednesday negotiations, and Spencer purposely kept himself out of these talks. But the role of Greenspan, representing Ford's interest after being named as Reagan's budget policy adviser, was ambiguous.

The prominent inclusion of Kissinger inflamed these conservative fears. There is no substantiation to reports that Ford wanted him back at the State Department in a Reagan-Ford administration. But for the man regarded by the right as a symbol of what was wrong with the Ford administration to be negotiating a delegation of Reagan's presidential powers was of questionable political wisdom.

Even if none of this represented a Ford Putsch, the idea of restructuring the presidency in a few hours of superheated convention climate was dubious. One Ford insider with business ties commented: "If General Steel thought of any such reorganization, they would do a two-year study by Booz, Allen and Hamilton [management consultant firm] before deciding anything."

Talk of Reagan as board chairman and Ford as chief operating officer reflected a desire by Ford to win the fruits of victory he dared not seek on the bloody battlefield of primary elections. But it also shows carelessness by Reagan about the august office. Indeed, amidst the euphoria sweeping the convention floor when the aborted deal was first reported, some instinctively knew it was wrong.

"If this is so good," asked Mississippi's national committeeman Clarke Reed, who defied his state's Republican opinion by backing Ford over Reagan in 1976, "why don't I feel better about it?" John Buckley, the veteran Massachusetts liberal Republican, told us: "This is terrible, very damaging for Reagan."

Ultimately, Ronald Reagan thought so, too. His supporters Thursday were rejoicing that he had the good sense not to enter so hasty a marriage that he might repent at leisure, and they admired his courage in coming to Joe Louis Arena to inform the delegates. About the rest of the affair, not much good could be said.