Weinberger asked: ''What happens after Marcos goes?'' ''It's not Iran,'' Habib replied. ''There is a democratic opposition backed by the Catholic Church.'' And, Shultz interposed, ''We have a great store of good will.'' Habib pressed: ''If we want some control over the situation, we must move fast to a transition.'' After a pause, Shultz declared: ''Our conclusion is unanimous. Now we need scenarios.''

Weinberger said, ''Without a new election I have trouble.'' ''You have trouble with everything,'' Shultz retorted. ''A new election is a must,'' Weinberger insisted. Gates interceded: ''Let's be realistic. The public view is that Aquino won. So we have to think of a way to install her in power and give Marcos a fig leaf to depart. Aquino in, Marcos out.''

Again Weinberger objected, submitting that Reagan would be distressed if he ''publicly appeared'' to be scuttling Marcos. Poindexter agreed. Someone advised doing nothing, to which Habib thundered: ''Give Marcos a chance to stay, and he'll hang on. He has to go!''

The same cast met in Shultz's office at 2 P.M. Bosworth was reporting that Marcos might soon attack the rebels, and a decision by Reagan was imperative. Charles Hill, Shultz's aide, had taken notes in his spidery handwriting at the morning session: ''Marcos can't govern . . . Forces favors left, bad for us . . . We have more options now than later . . . Do right by Marcos, departure in safety and dignity . . . Presidential phone call . . . Broker transition . . . Public call for no force.'' Using the notes, Shultz personally wrote a step-by-step script for Reagan, proposing that Laxalt and Habib fly to Manila with a Presidential message urging Marcos to quit.

At 3 o'clock, the group gathered in the White House Situation Room. Vice President Bush and Treasury Secretary James A. Baker 3d were there along with Casey. Reagan listened quietly as Don Regan hotly debated Habib. Regan, one participant recalled, ''didn't understand or care to understand'' the issue, but ''thought he was conveying Reagan's thoughts.'' Evoking Iran, he vehemently opposed dropping Marcos, called Aquino an unknown quantity and warned against ''opening the door to Communism.'' Habib repeated his case: ''The Marcos era has ended.'' Shultz concurred: ''Nobody believes that Marcos can remain in power. He's had it.''

Finally, Reagan seemed to be resigned to dropping Marcos, though he insisted the Philippine leader must be ''approached carefully'' and ''asked rather than told'' to depart. He declined to telephone him personally or send him a private message. But as the session closed, Reagan had acquiesced to deposing his ''old friend.''

Still, he and his staff were haunted by the prospect that Marcos might attack the rebels and slaughter civilians - on world television. Reagan approved an Administration statement warning Marcos that he ''would cause untold damage to the relationship between our two governments'' if he used force. But he kept secret his decision to tell Marcos to leave in the hope that he might go voluntarily and so be spared the embarrassment of being removed under American pressure.