Until last Thursday night, Theodore C. Sorensen believed that his nomination to head the U.S. intelligence community was opposed by only a small minority in the Senate.

"It was like being blind-sided by a truck," Sorensen said yesterday of his experience in watching the storm of opposition gather that led him to withdraw from consideration on Monday.

On Thursday, Sens. Joe Biden Jr. (D-Del.) and Howard H. Baker Jr. (R-Tenn.) received copies of affidavits Sorensen had provided in two trails involving the Pengtagon Papers.

Baker had requested the affidavits from the Justice Department Jan. 10, according to an aide.

Biden learned that the Republican committee members were seeking to use the affidavits against Sorensen and obtained his own copy through an aide who knew a participant in the Ellsberg trial who had kept files, an aide said.

Biden thought that a Republican committee member was likely to spring the affidavits during Sorensen's confirmation hearing and sought to preempt the Republicans by giving his copy to Intelligence Committee Chairman Daniel K. Inouye (D-Hawaii) for distribution to all members.

That night, Inouye called Vice President-elect Walter F. Mondale to tell him that the nomination was in trouble. Mondale passed the word to Sorensen and President-elect Jimmy Carter.

Sorensen tried to contact all the members of the committee Friday. His conversations with those who were in town "were for the most part friendly," he said. He said he did not realize that the nomination was in desperate trouble.

From his conversations, Sorensen said, he learned that "the affidavits were not the real reasons" for opposition to him.

What were the real reasons?

Sorensen is still not sure. The best explanatation, he believes, is that "many little dirty streams flowed together to make one large one."

Several committee members agreed that no single issue turned the tide against the nomination.

"If you thought there was a piece missing, how do you think I felt?" Sorensen asked in a telephone interview.

"I thought only Goldwater and two or three other conservatives would be against me," he said.

Sen. Barry Goldwater (R-Ariz.) refused to see Sorensen at any time after his nomination was announced Christmas Eve. When Sorensen was special counsel to President Kennedy, Goldwater made an issue of the fact that Sorensen had registered for non-combatant status with his draft board.

Sorensen said he saw all 14 other committee members at least once and met twice with several.

A source in the Carter-Mondale transition headquarters conceded yesterday a failure to move swiftly to counter the damage being done by the affidavits.

They state that Sorensen took classified information with him when he left the White House and used it in writing his book, "Kennedy."

That, Sen. Gary Hart (D-Colo.) said yesterday, was translated into that Sorensen was a leaker. His registration for noncombatant status became that he dodged the draft, Hart said of the torrent of criticism, much of it anonymous, fired against Sorensen over last weekend.

Several Senate staffers said that Minority Leader Baker played a leading role in organizing the criticism among Republicans and they were critical of reporters for allowing senators to make criticisms anonymously.

"This was a time when names should have been revealed," one said.

Before the storm broke on Capitol Hill, conservative groups were working to defeat Sorensen.

Steve Some of the American Conservative Union said that conservative columnist John Lofton had been doing a lot of research on Sorensen and "he began to get the ball rolling" as soon as the nomination was made.

On Jan. 10, the same day Baker asked the Justice Department for copies of Sorensen's affidavits, right-wing Rep. Larry McDonald (D-Ga.) chaired a meeting under ACU auspices.

Staff members representing committee members Sens. Jake Garn (R-Utah) and Strom Thurmond (R-S.C.) attended with ACU chairman Stan Evans and other conservative spokesmen, Some said.

"From this meeting came the strategy," he added.

"We had four senators right off the bat," Evans said, "Goldwater, Thurmond, Garn and [Robert] Morgan [D-N.C.]."

Then, Some said, it was decided to approach more moderate senators like Baker. "Baker was lined up on Friday," he said.

Other members were "lined up" by the already convinced senators, Some said. "Sen. Baker is very effective and it was better at that stage for us to get out of it," he added.

Evans refused to take too much credit for forcing Sorensen out. "In retrospect and modesty," he said, "it's conceivable that the Sorensen thing would have fallen through if we hadn't lifted a finger."

The ACU testimony against Sorensen was going to be delivered by Frank McNamara, who came out of retirement for that specific task. McNamara, a former chief administrative officer of the Subversive Activities Control Board and staff director of the House Un-American Activities Committee, said the affidavits were not his only grounds for opposing Sorensen.

In the Senate Foreign Relations Committee yesterday, outgoing CIA Director George Bush was lauded by several members for his performance.

Sen. Hubert H. Humphrey (D-Minn.) suggested that Bush might stay on for a while in view of Sorensen's withdrawal. Bush said his plan is to leave office at noon Thursday.

Sorensen's plan is to leave New York today for a Caribbean vacation.