As the Senate and House gear up for full-scale investigations into the Iran-contra affair, a leading Republican senator involved in the probe says every effort will be made to avoid turning it into a partisan vendetta. At the same time, Sen. Warren Rudman says, key figures in the Reagan administration, including the President, appear to have made major errors in judgment, for which they owe the American public a full explanation and an apology. In particular, says the New Hampshire senator, President Reagan should publicly accept responsibility for the entire affair, whether or not he knew of all the details in the Byzantine scheme.
Senator Rudman is but one of a number of influential Republicans who have been urging such a course on the White House. The President's Jan. 27 State of the Union address would be an excellent forum, he adds.
Rudman, who is vice-chairman of the Senate select committee investigating the secret sale of arms to Iran and the diversion of funds to Nicaraguan guerrillas, said that so far there has been strong cooperation between Republicans and Democrats on the Senate panel and with members of the counterpart committee in the House.
He indicated in a breakfast meeting with reporters that the Senate and House investigating committees, working with special prosecutor Lawrence Walsh, will jointly determine whether to grant immunity to people involved in the affair in exchange for their testimony.
The immunity question is something ``we'll have to start talking about ... sometime soon,'' said Rudman, who was formerly attorney general of New Hampshire.
But he voiced doubt that grants of immunity would by themselves thwart criminal convictions of any of the central figures in the affair. Such convictions, he said, may not be likely at any rate. ``There is not,'' he said, ``a punishment for every crime that is committed.''
``In this case ... you have to weigh the public interest [in learning the full truth of the matter] in terms of policy, in terms of oversight, against the slim possibility that somebody might ever get put in jail for this. ... I can tell you as a prosecutor it would be a pretty tough case.''
Rudman indicated that the investigation will be wide-ranging, covering ``the entire affair of shipping arms to Iran, and everything that flowed from that.''
He said the State Department had been advised that Congress might want to ask questions of ``foreign governments,'' presumably including Israel, to determine the origins of the arms-sale scheme. But he scoffed at the notion that Israel had somehow enticed the Reagan administration into the scheme.
``I don't care what anybody told this administration. They didn't have to do it. A lot of people give them dumb advice.
``The best minds in the administration were not listened to,'' he added.