The Iran-Contra affair will go down in history as the beginning of the end of the Reagan Administration's sway over American politics, Harvard professors said yesterday reacting to the Congressional report released Wednesday.

"Up until the Iran-Contra story broke, the image of the President was glowing and very positive," said Marvin L. Kalb, director of the Barone Center for Press, Politics and Public Policy at the Kennedy School of Government.

"The damage that was done to him as a result of this fiasco was very major and lasting," Kalb said. "When historians look back, they will see the administration in terms of pre-Iran scandal and post-Iran scandal."

The report, issued by the joint Senate and House committee investigating the matter, said that President Reagan was ultimately responsible for the affair, but it absolved him of any effort to deceive Congress.

"I think [the affair] marked the end of the Reagan Administration," said Assistant Professor of Government Laurie Mylroie. "It's going to be a black mark. It's not going to be forgotten."

Although they were not surprised by any of the information or conclusions of the report, the professors interviewed said it could cast a pall over the remainder of the President's term.

"I think people forget things really quickly, and being reminded of all this again will have an adverse impact on the President's standing," said Professor of Government James E. Alt.

While the impact on next year's Presidential election is uncertain, the professors said the damage could extend to the Republican Party as a whole.

"It's hard to see how [the scandal] could help any Republican candidate," said Alt.

But the profesors agreed that the chief casualty was President Reagan.

The affair "has diminished his stature and raised questions about his competence," Kalb said. Reagan's "hands-off attitude was bordering on the irresponsible."

Benjamin I. Schwartz '38, Williams Professor of History and Political Science Emeritus, criticized Reagan's "unjustified and arbitrary use of presidential power" and "executive irresponsibility" during the scandal.

The scandal not only was harmful to the Reagan Administration, said Mylroie, but it "was a disgracc to this country's foreign policy."