If embarrassment is radioactive, President Reagan should have stayed on the "doomsday" plane that brought him back from his turkey-shooting weekend in Texas.

He got off the "doomsday"--which in the event of enemy attack would carry him high above the battle--and stepped into the fallout of proliferating personnel problems.

He has a budget director who doesn't believe in supply-side economics, a national security adviser who takes money from Japanese journalists for exclusive interviews with the First Lady, and a secretary of state who seems to want to start a war in Central America.

The heretic, the arranger, and the warmonger are all, for the moment, still at their posts, in what the president calls the "happy group" at the White House.

Budget director David A. Stockman got a presidential lecture for having committed the sin of intellectual pride. He could not resist communing with an intellectual peer, William Greider, a Washington Post editor. Stockman, from the compulsion of the ultra-bright, had to let Greider know that he knew what was really going on.

The conditions for publication in The Atlantic Monthly of their extraordinary, periodic exchanges were fuzzy, but Stockman was thinking of his place in history rather than in the Reagan administration, as he confided his wrong numbers, political miscalculations and "Trojan Horse" theory of the tax cut.

The article sent the Democrats into ecstasy. At the dinner where they gathered to hail the survival of Averell Harriman to his 90th year, they toasted Stockman and the revival of their party.

Young Stockman can go no more to Congress and argue against widows and orphans--and not just because of the exulting Democrats. Senate Majority Leader Howard H. Baker Jr. (R-Tenn.) said morosely that Stockman has "caused serious political problems for Republicans."

The case of Richard V. Allen broke two days later, with the astounding intelligence that the national security adviser had "received"--he indignantly rejected the word "accepted"--$1,000 in cash from a party of Japanese who, as a result of his intervention, had an interview with Nancy Reagan the day after the inauguration.

Allen, whose previous business dealings with the Japanese as recounted in the Wall Street Journal had caused his brief suspension from the Reagan campaign, says it is "an old Japanese custom" to express "gratitude" to sources. From Tokyo have come denials of such a tradition, and a dispute rages as to whether the $1,000 was solicited or volunteered.

At first, Allen categorically denied he had "arranged" the interview, then conceded he had "fielded the request," which came from an old friend in Japan, whose wife was interpreter for a brief session which Mrs. Reagan cannot remember having taken place.

The White House was full of chat in the first hours after the incident, which came to its attention from Tokyo, where Japanese police are "cooperating" with a U.S. investigation.

The president, hardly audible over the whir of the helicopter waiting to take him to Texas, said Friday night, "As far as I know there is no evidence of any wrongdoing."

But by yesterday, having discovered that the Justice Department investigation, which White House counsel Fred Fielding had prematurely said was closed, was continuing, the wagons had been circled. At the regular noon briefing, White House deputy press secretary Larry Speakes said "no comment" to the many queries assailing him. The only question he answered was as to whether Allen would be at the National Security Council briefing. Yes, he would.

It got so sticky that Speakes visibly welcomed a question about the economy which, of course, is getting worse by the hour. When Secretary of State Alexander M. Haig Jr. whined recently that someone in the White House was out to get him, the president said he doubted the existence of such a person and would make no search. But in the Allen affair, it seems inescapable that someone was out to get Haig's nemesis. A "secretary," we are told, found the $1,000 in Allen's old safe. A true helpmate would have taken it to him and said, "You forgot this." Instead, that person called the cops.

But Stockman's indiscretion and Allen's folly fade beside the insubordination of the secretary of state. Haig has his own foreign policy, as he arrogantly told a House Foreign Affairs Committee. Two days after the president announced he had no plans for "putting Americans in combat any place in the world," Haig defiantly refused to rule out military action in Cuba and Nicaragua. The president's statement, he said condescendingly, "should stand" but he is waging a war of nerves against Cuba and Nicaragua and needs the threat weapon.

The president's forbearance in the face of such provocations makes him a strong contender for the "Boss of the Year" award, but it doesn't do much else for him.