WASHINGTON -- Senate Majority Leader George J. Mitchell disclosed yesterday that he will not be named to the Supreme Court -- a surprise ending to a swift turn of events that will keep the lawmaker in the Senate the rest of this year.

In the end, Mr. Mitchell and President Clinton reached an understanding that the Maine Democrat will finish out his term, through early January, to help push through the president's legislative program, including health care reform.

The senator and the president commented at length yesterday on what had happened, but some variations in their accounts left unclear the details of the sudden switch.

The senator told reporters at the Capitol that he and Mr. Clinton discussed the Supreme Court vacancy for the first time in a meeting at the White House Monday evening, and the president had said "that he wanted to appoint me to the court, that he intended to appoint me to the court" to replace retiring Justice Harry A. Blackmun.

But, Mr. Mitchell went on, the president expressed worry about how the appointment now would affect the majority leader's ability to carry out his Senate duties. The senator said that he, too, had been wondering about that, since press reports indicated that he was the front-runner for the court nomination. He said the Monday meeting was his idea, to put his concerns to the president.

He carried with him, he said, a withdrawal statement, which Mr.

Clinton read. After their discussion, he said, the president said both should think about it overnight, which they did, leading the president "reluctantly" to go along with the withdrawal yesterday.

The president's version, given at a White House reception after Mr. Mitchell's disclosures, differed somewhat. He said Mr. Mitchell had come to the White House and asked "what I wanted him to do." Mr. Clinton said he replied that he merely wanted to "talk to you about" the vacancy.

Then, Mr. Clinton went on, he told the senator: "I'd like to appoint you to the Supreme Court if you think we can do our work here for the country this year in pursuing health care reform and the other things we have to do."

Ultimately, the president recalled, Mr. Mitchell said: "I believe I should stay in the Senate and serve my term out and try to lead this country to health care reform." Mr. Clinton's version, like Mr. Mitchell's, included their discussion about sleeping on the issue, followed by yesterday's phone conversation producing agreement that the Senate Democratic leader would stay where he is.

White House press secretary Dee Dee Myers dismissed as "absolutely incorrect" a reporter's speculation that Mr. Mitchell might have been nudged out of the running for a Supreme Court seat that he had seemed to want strongly. A senior White House official, who declined to be identified, said that Mr. Mitchell "absolutely" was not edged out; the official added: "The job was his if he wanted it."

Whatever happened behind the scenes over the 24 hours before yesterday's disclosures, it was clear that expectations held as recently as last weekend had been shattered. Then, it appeared that Mr. Mitchell would be chosen for the court, that his nomination would move swiftly through the Senate and that arrangements would be made to let him lead the Senate until most of the White House's major legislative goals this session had been met.

All that was left behind at noon yesterday with Mr. Mitchell's news conference. White House officials put out the word that the president was surprised and disappointed but indicated that Mr. Clinton had decided to let Mr. Mitchell make the choice and then agreed with it.

Through the rest of the day yesterday, the White House issued a series of flattering comments about Mr. Mitchell's personal sacrifice.

The developments appeared likely to delay the White House process of picking a successor to Justice Blackmun and to increase the chance that the seat would go to a black or Hispanic candidate, partly as a symbolic gesture of diversity.

The president's reported "short list" -- which may be expanded -- includes two blacks: U.S. Circuit Judge Amalya L. Kearse of New York City, who is 56, and U.S. Solicitor General Drew S. Days III, 52; and at least one Hispanic-American, U.S. District Judge Jose A. Cabranes, 53, of New Haven, Conn.

Judge Kearse, who would be the first black woman to become a justice, has strong support from the National Political Congress of Black Women. That group reminded the White House this week that black women gave Mr. Clinton 86 percent of their vote in 1992, "the highest percentage of any group."

There has never been a Hispanic on the court, and the president is under considerable pressure from Hispanic-American groups to name such a justice -- with the reminder that Mr. Clinton's standing with that constituency will become vital to his chances of winning California in the 1996 presidential contest.

Friend of Clinton

Another name on the supposedly preferred list is that of the president's longtime friend, U.S. Circuit Judge Richard S. Arnold of Little Rock, 58, who is white.

Mr. Mitchell apparently had been at the head of the list, and events since Justice Blackmun's retirement a week ago appeared to be unfolding toward the Maine lawmaker's nomination. Yesterday, a day after the president had had his first discussion with the White House staff about a successor to Justice Blackmun, Mr. Mitchell revealed that his selection was not to be. Rather than a Supreme Court justice, he may wind up as the commissioner of baseball -- an offer that has not been made but that the senator said yesterday he would consider.

Although the senator is retiring from the Senate in January, at the end of his term, he said he regarded the rest of this year as crucial to health care reform. "I don't think that opportunity is going to come along again at any time in the future if we don't seize it this year," he said.

Mr. Mitchell said that if a Supreme Court vacancy was offered to him in the future, he would consider it. The Maine senator has said privately that, if he were to join the court, he would be interested primarily in becoming chief justice.