The bitter explosion of accusations between President Carter and Sen. Edward M. Kennedy was fueled by a single paragraph in Kennedy's Harvard speech that had attracted only moderate public attention, but dominated an angry meeting in the Oval Office. m

The morning newspapers had not focused upon the paragraph in their Wednesday stories. Neither had two of the television networks in their broadcasts the night before. But CBS had shown Kennedy speaking the three controversial sentences -- and the president had seen the show, and in case his advisers had missed it, a transcript of the Kennedy segment had been circulated among them. And by the time of their 10 a.m. meeting with their boss, they were, all of them, angry.

At Harvard University on Tuesday, Kennedy had said:

"And for months, the White House rejected a commission on Iranian grievances -- which could have freed the hostages sooner. Now, at last, the president is about a agree to it. But the administration stubbornly resisted this solution until I and others made the proposal and broke the silence on Iran."

The next day, the White House began to orchestrate a series of angry denuciations of Kennedy -- beginning with spokesmen at the White House and State Department, then with Democratic National Committee Chairman John Hite, next a more moderate and diplomatic rebuke from Secretary of State Cyrus r. Vance, and finally a news conference denunciation from Carter himself that was perhaps the harshest attack that a president has made upon a political rival in recent times.

Kennedy was accused of making statements that were "false" and "erroneous" -- and it was said Kennedy knew the facts of the administration's negotiation effort because he had been briefed by the secretary of state and secretary of defense, as well as United Nations Secretary General Kurt Waldheim, just before Kennedy made his own Iranian crisis proposals last month.

So the central question came down to a variation on a familiar theme: What did the senator know and when did he know it?

Actually, according to one of Kennedy's chief advisers, the Massachusetts senator's sweeping statement that "for months the White House rejected a commission on Iranian grievances" is not accurate.

In fact, he conceded, the senator was aware that the administration was working toward a variety of solutions that would involve creation of an international commission on Iranian grievances.

The real question, according to this adviser, who would not agree to be identified by name, was whether the administration was prepared to agree to the estiblishment of an international commission to investigate the regime of now-deposed Shah Mohammad Reza Phlavi prior to the release of the Americans being held hostages.

"There was not a single thing they said in any briefing we went to that the administration was prepared to go ahead with the commission in advance of the hostages being released," according to this Kennedy adviser. He said that at Kennedy's Jan. 26 meeting with Vance, notes of what was said were taken by Deputy Secretary of State Warren Christopher and Kennedy's adviser, Jan Kalicki.

Said the Kennedy adviser:

"The picture that Sen. Kennedy received was that the administration wanted to go ahead with economic sanctions [against Iran -- a position the administration has since pulled back from], and that they would not agree to establish a commission before the hostages were released."

The Kennedy adviser added that after Carter had met with Waldhelm, "it was our understanding that the president was prepared to go so far as to agree to a simultaneous setting up of commission and the release of the hostages."

Kennedy, however, had proposed that the United States go further. In his Jan. 28 speech at Georgetown University, Kennedy called for a three-step process: first an international commission would be created, then the hostages would be released from Iran, and finally the commission would begin to function.

That, the Kennedy adviser said, was what Kennedy meant when he blasted the Carter administration for having "stubbornly resisted this solution until I and others made the proposal . . ."

Meanwhile, yesterday, State Department spokesman Hodding Carter said in an interview that "the whole premise of what Sen. Kennedy has said was that we were not prepared and not willing to consider an international commission -- and that is wrong. . . . We had indicated to him [in the Kennedy-Vance briefing] that we were suggesting a commission . . . that we were saying at first that the commision would not be formed before the hostages were released, and then later we were saying that the two could be done simultaneously."

Such is the fallout of the harsh political exchange born out of campaignstump rhetoric that was admittedly lacking in detail, and probably (but not admittedly) excessive as well.

The thrust of Kennedy's remarks was that Carter had refused to move on the idea of an international commission until Kennedy had shown him the way. And that is what the Carter inner circle was so angry about when it was joined, in the Oval Office, at 10 a.m. Wednesday.

Stuart Eizenstat was among the most indignant. "Kennedy's telling untruths now, and he must be responded to," Eizenstat said, according to another presidential advisor who was present.

Others in the room were quick to agree. This was not a difficult position to take in the president's presence -- most of the advisers had already heard, by word of mouth, just how angered Carter has been by Kennedy's comments.

The quick consesus was that it was bad enough that Kennedy was trying to take credit for a commission concept that the administration had been working on since November. "But the worst thing was the he was trying to say that the United States government was intransigent," according to one Carter adviser.

"The feeling was that, 'This is more than we can allow; if we allow it to go unanswered, it will only get more irresponsible.'"

This was the origin of the admisistration's decision to retaliate in an unprecedented barrage of counterrhetoric. Kennedy was attacked with all the subtlety of anvils dropping from skyscrapers. And when they were done, the Carter officials has performed an anvil's chorus of unmistakable resonance. A chief architect was press secretary Jody Powell, who was on the phone to Hodding Carter at State almost as soon as the meeting with the president had ended.

When, in midday, there was lull to the criticism, the White House made it clear to the State Department that the president would like the secretary to personally deliver a blast of his own. And this, too, was done.

Finally, at his nighttime news conference, Carter accused Kennedy of "damaging" the national interest and the effort to free the hostages by making "erroneous" and "false" statements.

The effect of the Carter barrage was perhaps more harsh than any recent exchanges between presidents and their political adversaries, more so that the Vietnam-era exchanges between Nixon and McGovern, and Johnson and McCarthy and Robert Kennedy and Nixon.

And the result of the charge and countercharge was to create precisely the sort of situation that Carter had maintained all along he wanted to avoid. It was the reason he would not campaign or debate, he had said. And his wife, Rosalynn, explained it all clearly on Jan. 31 in Bufflo, saying:

"The appearance of disuntity is exactly what the Iranians and the Soviets want. To see a president arguing or debating on any issue appears to other people, in other countries who don't know our political situation, that we are disunited in our country."