On Thursday, in a vote that pleasantly dumb-founded supporters of the measure, the House followed the Senate in approving $75 million for Nicaragua in economic aid. This was, politically speaking, the litmus-test item in the big foreign aid bill for which the House authorized overall $5.2 billion, just about what the administration had sought. And this in a year of a painfully tight budget and much foreign policy frustration.

The Cuban past seemed to hover, as a specter, over the Nicaragua debate. The question was whether, by a timely offer of good will for the government and concrete assistance for the moderates and the business class, the United States might help steer the Nicaraguan revolution, which has a heavy leftist component, in the direction of an open society. It is a gamble but, in a sudden and quite unexpected surrender to the logic of the argument, the House decided to take it by a vote of 221 to 147. Speaker O'Neill delivered what he described as his first floor speech for foreign aid in 28 years. He had been impressed, he said, by the assurances of Nicaragua's devotion to freedom and independence given by Arturo Cruz. A junta member and banker. Mr. Cruz had been invited to Washington for this debate by the Council of the Americas, a business group that, with other private organizations, was instrumental in helping the administration lobby the Nicaragua item through.

For the prickly new leadership of Nicaragua, brought up with a vast distrust of American power, this display of American enlightenment is not easy to handle. Both the Sandinistas and their two (minority) partner in the ruling junta resented Speaker O'Neill's earlier statement, for instance, that aid would be put on hold until the junta replaced two moderate members who had resigned. The junta wanted it known that it would not succumb to any American pressure. But on its own initiative, of course, it did find two new moderates, including Mr. Cruz. Mr. O'Neill then came through handsomely, Thursday on the floor.

When the Sandinistas were still fighting in the hills, they probably didn't dream that once they took power they would be making key political decisions in a complicated, unacknowledged negotiation with Tip O'Neill. But they are adapting. So is he and so are his house colleagues. it is the kind of politics that makes sense for both sides.