It was 2 a.m. Dec 21, the last vote in Congress in the 1970s. The weary House had already gone home for Christmas. But on the Senate floor, the two old men were still pounding at each other in their own Late Late Show, a flashback to the civil rights battles they had helped fight 20 years before.

The senators were New York's Jacob K. Javits, 75, and Mississippi's John C. Stennis, 78. The issue dividing them was President Carter's nomination of L. T. Senter Jr. to be federal judge for the northern district of Mississippi. And the vote was dramatic proof of the civil rights lobby's loss of power in the last 10 years. A judge accused of racist behavior was confirmed by the Senate nearly 2 to 1.

This was no ordinary nomination. Blacks in Mississippi, a state notoriously repressive in its treatment of black citizens, rely to an unusual degree on the federal courts for equal justice. To them the northern district of Mississippi is the most important court in the land. The retiring judge, Orma Smith, has a strong pro-civil rights record.

And though Senter was not opposed by all blacks -- not, for example, by the state's most respected civil rights figure, Aaron Henry -- to many blacks he looked like bad news.

Senter has been a state circuit judge for 10 years. There was testimony, which he denied, that Senter often used the term "nigger" on the bench. He has transferred his children from public schools to an all-white private academy when the public schools were ordered -- by a federal judge -- to desegregate. Only recently had he resigned from an all-white club.

Javits, leading the fight on the floor, noted that at age 46 Senter could reasonably expect to sit on the federal bench for the next 30 years.

"I hope he lives forever," Javits told the Senate, "but that is an awful long time to confirm him for at one o'clock in the morning" with no record for senators to base a vote on. The Judiciary Committee hearings on Senter had not been printed, and no committee report was available. The committee had approved him by an 11-to-6 vote only 12 hours earlier.

But Stennis, who had personally chosen Senter for the judgeship and recommended him to Carter, was determined to have a vote; delay could give the opposition time to build up.

And the powerful Mississippian Senate patriarch, chairman of both the Armed Services Committee and the Appropriations subcommittee on defense, had his way.

The administration was with him; so were Majority Leader Robert C. Byrd (D-W.Va.) and others in the Senate leadership. The liberals were disorganized, late to the fray and divided.

Carter's rival for the Democratic presidential nomination, Edward M. Kennedy (D-Mass.), voted against Senter in the Judiciary Committee, of which Kennedy is chairman.

But Kennedy was gone campaigning when the Senter nomination reached the floor. Other liberals also were gone, or voted with Stennis. Most senators had no idea where the truth lay, but on that early morning four days before Christmas they were more willing to go with Stennis than to heed protests that the record was at best ambiguous and needed more consideration.

There would not have been that same indifference 10 years ago. Joseph L. Rauh Jr., a Washington lawyer who has been on the leading edge of every civil rights fight for the past generation, admits it. He said he heard about the Senter nomination only 48 hours before the Senate vote and then it was too late to defeat it.

Marian Wright Edelman, who worked in the civil rights movement in Mississippi in the 1960s, said the Senter issue seemed to fall into cracks, with everyone thinking someone else was doing something about it. That would not have happened in years past. Rauh and the NAACP's recently retired chief lobbyist, Clarence Mitchell, would have been all over Capitol Hill raising hell, and the Leadership Conference on Civil Rights would have been throwing its considerable weight around.

On the other hand, this appearance of a civil rights defeat, of the South placing one of its own on the federal bench, may actually cover up an agreement or understanding that the next federal judge named in Mississippi will be black. That could happen this year.One newsman who covers the area is convinced it will happen.

That could explain the Carter acceptance of Senter despite his pledge to name more black judges in the South, the lack of a Kennedy attempt to block the nomination, and the refusal of Aaron Henry to oppose Senter.

Sen. Charles McC. Mathias (R-Md.) voted "yes" in committee, in good part because Aaron Henry did not oppose Senter. But 12 hours later Mathias voted against Senter on the Senate floor because he learned something that raised a question of credibility. Senter had told the Judiciary Committee he didn't know that the private academy to which he transferred his children had lost its tax exemption because it refused to promise not to discriminate. When Mathias learned that the tax case had received extensive press coverage in the area, he simply couldn't believe Senter.

The search for a new judge for northern Mississippi began early last year after Smith announced plans to retire from fulltime duty. Rather than have candidates screened by a merit selection committee as is the practice in most states, Stennis told Carter he wanted to select the nominee himself because the district included the area where he had been a state judge for 10 years before coming to the Senate 32 years ago. Carter agreed after Stennis agreed to consider all qualified persons regardless of race or sex.

By midyear, Stennis selected Senter, whom he had not known previously. The American Bar Association's committee on the federal judiciary found him qualified for the federal bench by a split vote. It was not until the first of October that the Justice Department completed its investigation of Senter and his name was sent to the Senate for confirmation. The Judiciary Committee conducted a hearing that lasted about four hours on Nov. 29 and approved him at a special meeting called on the afternoon of Dec. 20.

Stennis told the commiteee he had asked Aaron Henry to submit recommendations and had personally interviewed each one. After Stennis concluded that Senter was the best qualified, he ran Senter's name past Henry, who did not oppose it.

But opposition was instant among some other Mississippi blacks. They voiced charges of racial slurs on the bench, transfering his children to avoid integrated schools, and belonging to an all-white club.

There was also an old story that in 1947 at age 14, Senter had been in a mob that castrated a black suspected of assaulting a white woman. Opponents made much of this at the committee hearing. But the victim was found in Michigan, not castrated and denying that Senter was in the mob. The explosion of this charge may have left a cloud over the rest.

A young white Mississippi lawyer who had been a legal intern at Senter's court several years ago testified that Senter often used the term "nigger" on the bench. Senter flatly denied it. "Absolutely not true," he told the committee. "I have never made racial slurs on or off the bench."

Senter told the committee he transferred his children because his older son needed more help than crowded public schools could offer. Year before last he sent his two younger children back to public schools. Opponents suggested he was looking ahead to a federal judgeship.

Senter conceded there were no black members in his private club, though he said he felt no air of discrimination there. He quit, he said, because he was aware of the committee's feeling on the subject and thought "it would alleviate the situation and save time" if he quit before being told to do so.

"I have tried to run my court in a fair and impartial manner with equal justice for all people regardless of race," Senter told the Senate committee. "I will attempt to run the court in an honorable and fair way for all people who come before me."

Mayor Bennett Thompson, 31, of Bolton, speaking for the Mississippi Conference of Black Mayors, which has 19 members, told the committee:

"The political structure of Mississippi rests virtually unchanged and unresponsive to the needs of blacks. Therefore our only source of relief has been through the federal courts. Judge Senter does not enjoy the confidence of many blacks in the state."

Frank Parker, white lawyer in the Mississippi office of the Lawyers' Committee for Civil Rights Under Law, also spoke of the importance of the court to blacks. The two sitting judges in northern Mississippi have shown "exceptional fairness and sensitivity in handling civil rights cases," said Parker. Judge Smith, whom Senter would replace, "has truly been an inspiration to me as an attorney handling civil rights cases in his dedication to enforcing the Constitution and civil rights laws."

"It is because of this great tradition," Parker told the committee, "that those of us in the civil rights community were particularly dismayed and disheartened when we learned of President Carter's decision to nominate Judge Senter. It is my view that Judge Senter fails to meet the qualifications . . . a demonstrated compassion and sensitivity to human rights and civil rights of black citizens."

Parker called withdrawal of Senter's children from public schools an "act of blatant racism."

Senter had been elected to the state court three time, twice in contested elections, in an area that is about half black. He told the committee he wouldn't have done anything to alienate their vote and wouldn't have won if he had.

When the committee met on Dec. 20 to vote, Sen. Max Baucus (D-Mont.) told colleagues he had been troubled by the Senter case and had telephoned the judge a few days earlier in hopes of easing his mind. He said he was even more disturbed after their talk. Baucus had hoped to move the conversation beyond the specific charges and hear Senter agree that there was an affirmative need for sensitivity to black problems. Baucus didn't feel he got such a response and voted against confirmation.

Even after the committee approved Senter, it seemed unlikely that the Senate would act on him before quitting for the year. Javits, who had played a leading role in all the Senate civil rights battles since 1957, served notice he would object to a Senate vote that day. Under the rules unanimous consent was required in order to bring it up the same day it was reported from committee.

The Senate was expected to quit that day and Majority Leader Byrd obtained unanimous consent that all nominations not yet acted on would stay alive in the 1980 session. Otheriwise, they would have to be resubmitted.

But final action on the Chrysler bailout bill which was holding Congress in session took longer than expected. The Chrysler vote was delayed until after midnight. Javits' "same-day" objection was wiped out and Byrd called up the Senter nomination.

In debate, Javits told the Senate that "very serious charges" had been made and that the nomination should be held over the next session beginning Jan. 22 to give senators time to read the record. "A state judge who utters racial slurs on the bench is clearly not qualified for elevation to the federal bench," said Javits.

Sen. Birch Bayh (D-Ind.), acting Judiciary chairman, rose: "I have to say the record on the pending nomination is ambiguous. I think there are sufficient questions to cause deep concern, sufficient questions to cause me to stand here at a very disagreeable hour and undertake a very disagreeable task."

He recited the testimony and said; "There are just too many unanswered questions . . . I would like to have more information before I vote to put this man on the federal bench for life."

In response to a colleague's question, Bayh said there was no evidence that, in his rulings as a state judge, Senter showed prejudice.

Stennis summing up, seemed astonished at the opposition that had developed. "It is just impossible," boomed Stennis from his desk at the center aisle, "for all this stuff to have been true without my learning something about it before I ever made the selection."

Stennis also told Javits and the rest that use of the term "nigger" shouldn't be considered all that bad:

"I tell you, this word 'nigger,' I have lived with them all my life and in years past I have heard many of them call each other 'nigger' and that was not such a bad term then. But all mothers taught their children not to call the blacks 'black.' The blacks considered that a slur. I was taught 'don't call them black. Be respectful to them.' Well now they want to be called black. My point is these things change, customs change. The word being thrown around some is not necessarily an insult, in earlier days not anyway."

And then they voted. Senter was firmed 43 to 25. A third of the Senate was already gone.