WHEN HE FIRST heard about it, Sen. Charles McC. Mathias (R-Md.) advised the White House to delay the appointment of Kenneth Adelman to succeed Eugene V. Rostow as chief of the Arms Control and Disarmament Agency. He warned that the naming of the prolific young hawk would precipitate a policy debate about disarmament that would better occur before Adelman came before the Senate Foreign Relations Committee.

That is, of course, exactly what happened, and the Senate Foreign Relations Committee unexpectedly voted to delay the nomination. The president, as his press conference, took it personally. And he was right to do so. A vote of "no confidence" in his disarmament policies had taken place.

Adelman was a "zero option" choice to begin with. He had written and spoken copiously about the dangers of dealing with the Soviets. At his first appearance, on Jan. 27, he astonished the Foreign Relations Committee by refusing to say a bad word against nuclear war. Although housewives and town clerks have registered through numerous freeze votes doubts about "limited nuclear war" and other Reaganesque formulations, Jeane Kirkpatrick's U.N. deputy had "never thought" about them.

At his second coming, eight days later, Adelman had been given a new game plan by his coaches, and he declared unequivocally that the consequences of nuclear war would be "horrendous."

It was enough, said local wise men, to clinch the nomination. The president's right to his own appointees is respected in both parties and transcends the obvious affront to peace groups.

The plaints of Sen. Larry Pressler (R-S.D.) that the committee had not been consulted and that the choice was "devastating" were ignored. The White House felt, on the basis of past experience, that Pressler is a killer rabbit among enemies. When he opposed the sale of AWAC's to Saudi Arabia, the president's people flew in Maxwell Rabb, our ambassador to Italy, who is Pressler's counsel on Jewish affairs. After a breakfast with Rabb, Pressler reversed himself and supported the administration.

But Pressler's rabbi on disarmament is Eugene V. Rostow, who was dished by Reagan for reasons never adequately explained. Pressler asked that Rostow be brought before the committee to testify. Rostow declined, but not apparently to give his views on Adelman to Pressler.

In any case, Pressler announced he would vote against Adelman. After the president hold his press conference the Senate rejection would be "destructive" to our allies, Pressler said he would vote against the nomination if the president persisted in his intention to bring Adelman to the floor.

"If he insists, the president can get Adelman confirmed," Pressler said the day after the showdown in the Senate Foreign Relations Committee. "I will vote against him."

Sen. Alan Cranston (D-Calif.) the point man against Adelman, precipitated the showdown by suggesting the Adelman be called back for a third session. Cranston said that new evidence -- a New York Daily News interview by Ken Auletta, in which Adelman calls arms control "a sham" to placate our allies -- justified his motion.

Sen. Paul Tsongas (D-Mass.) offered the president a face-saver. He called for a week's delay, obviously time enough for Reagan to take down the offensive nomination. It passed by voice vote.

Reagan is now back to square one on arms control credibility.

The Adelman nomination reignited all the suspicions at home and abroad that he cannot bring himself to negotiate with the Russians.

In the wake of the Rostow sacking, White House apologists tried to explain that the selection of a biddable junior showed only that Secretary of State George Shultz, a calm, avuncular presence, would himself take personal, total charge of the whole troubled disarmament question, even though he had never said a word about the subject in public.

That comforting notion was hardly reinforced by Shultz' subsequent, immediate departure on an extended tour of the Far East. It would have been unthinkable to cancel his long planned trip to China. Reagan was forced to resurrect Vice President Bush, who has been all but buried alive in the administration, and send him on a high-profile rescue mission to European capitals.

Bush came back saying on the one hand that our NATO allies approve the non-starter "zero option" proposal, and on the other that they favor an "interim solution."

His most effective moment, at least on television, occurred when after a brush with demonstrators, he rhetorically asked a London gathering, "Don't you think we want peace as much as they do?"

The answer, once again, from Capitol Hill and elsewhere, seems to be, in Ronald Reagan's case, "No."