Washington — Sen. Harrison A. Williams's rambling, lackluster pleadings of innocence won few defenders on the floor of the US Senate. How could his fellow senators speak up for a man whose crimes are recorded on Federal Bureau of Investigation videotape?
But his charge that the FBI deliberately lured him into bribery will linger on Capitol Hill now that the New Jersey Democrat has resigned his seat. Mr. Williams is already claiming a victory of sorts because former colleagues have called for an investigation of the FBI's Abscam probe that snared Williams and six members of the House.
Two years after news of Abscam first leaked to the press, many of the questions surrounding the investigation still have not been fully answered. Sen. Alan Cranston (D) of California, who leads the charge against Abscam, has told reporters that wrongdoing of ''the magnitude of Watergate'' is involved. He stops short of blaming a president.
Senator Cranston, who is the Democratic whip, has joined forces with Sen. Ted Stevens (R) of Alaska in pushing for a probe of the FBI's undercover practices.
Not only does Mr. Cranston charge the FBI with the ''grossest conduct'' in Abscam, but he warns that an unscrupulous executive could ''threaten the independence of Congress'' by launching such investigations.
Among the major Abscam questions:
* Did the FBI try to tempt congressmen to take bribes when it had no prior evidence that the lawmakers were ''on the take''? Cranston cites an October 1981 Justice Department brief stating that ''undercover operatives do not need probable cause, or even reasonable suspicion, to commence an investigation.''
Of special concern to senators has been the case of Sen. Larry Pressler (R) of South Dakota, who was invited by undercover agents to a Washington town house and offered a bribe by a man disguised as an Arab sheikh while a hidden camera recorded the event. He turned the bribe down flatly.
Sen. David Pryor (D) of Arkansas expressed shock last week as he revealed that FBI Director William H. Webster had personally authorized the bribe offer to Senator Pressler on very short notice.
* Did the FBI lose control of its own agents and employees during the the probe? Cranston charges that the chief undercover operator, convicted con-man Mel Weinberg, ''was totally out of control'' in Abscam.
* What led the FBI to start investigating members of Congress in the first place? Could a political motive be involved?
Responding to the congressional critics, FBI spokesman Roger Young told the Monitor last week, ''We are willing and able to fully defend the Abscam operation.'' He noted that there are ''a lot of unanswered questions and misunderstanding'' about Abscam.
On how the FBI runs its probes, he said, ''We had no desire to bring in congressmen or anyone who was honest and was not interested in meeting with these kinds of people (who would offer a bribe).'' He said the FBI used a two-prong test in selecting targets.
First, the investigators relied on ''middlemen,'' corrupt influence peddlers, to tell undercover FBI agents which public officials take bribes. These middlemen are not government agents and do not realize they are dealing with the FBI, but they usually provided reliable tips in Abscam, Mr. Young said.
Second, the Abscam investigators had a rule that no bribe money would be offered until agents made it clear that they were offering a bribe in return for a service. So there could be ''no misunderstanding,'' he added.
In the Pressler case, his name popped up at the last minute as a substitute for another congressman. It did not come directly from the middleman.
Young dismissed any charge that politics had a role in picking targets or in the decision to probe Congress. ''Abscam began as a low-level sting-type operation aimed at stolen art and stocks and bonds,'' he said, and the middlemen involved began naming congressmen.
Senator Pressler predicts that the Senate's Abscam probe will be a low-keyed effort that will produce a study a year from now when most people have forgotten Abscam.