Two parties for two men:

One was all dark suits and book business. The other was sequin dresses and red heart-shaped balloons. Both celebrated Democrats and both had a touch of tough talk about the hijacked Italian cruise ship.

Especially Sen. Gary Hart (at the heart-shaped balloon party, of course), who had this advice for President Reagan in dealing with terrorism: "As long as we remain passive, we'll remain victims. I think we ought to infiltrate terrorist groups. I think we ought to anticipate these things and head them off."

At first, Hart was not the main attraction, or even No. 2, at the balloon party, actually a fundraiser thrown by Pamela Harriman at her Georgetown house to help Hart erase his old campaign debts.

"I'd like you to meet our most famous Minnesotan," said one of a large number of bleached blonds. She was speaking to actor Jack Nicholson, and she seemed bolted to the floor at his side.

"I already know one," he said, with that leering Nicholson smile.

"Who is it then?" she said.

"Jessica Lange," he said, with that sneering Nicholson laugh.

"No, Walter Mondale."

And so Walter Mondale, attendee at both of last night's parties, walked up to Jack Nicholson, in town shooting "Heartburn," and shook his hand. Actor meeting politician, or something like that.

"I'm a great admirer of yours," said one to the other. (You guess who said it to whom.) "Except you supported Hart instead of me."

"At least we Hart supporters didn't drop out on you like everyone else did," Nicholson said. He's been a Hart supporter for more than 10 years and a Democrat for much longer. But not a choosy Democrat.

"Any of those last six candidates would have done it," said Nicholson.

Harriman said the party raised about $200,000 to help reduce Hart's debts, but there was more talk of Hart readying for '88 than of erasing '84. Comments like "See you in the White House" were frequent and fast.

And at the other party, the book talk was, well, book talk:

"How do you want me to sign this?" asked Sol Linowitz, author of his memoirs. "To whatchamacallit? To Walter something or other?"

To which Mondale replied, "Yes, that's spelled M-O-N . . . "

A joking Defense Secretary Caspar Weinberger embraced Linowitz, author of "The Making of a Public Man," including his years as chairman of Xerox Corp., Middle East negotiator in the Carter administration and Lyndon Johnson's ambassador to the Organization of American States, and said, facetiously, "Tell me, how did you love my book?"

Predictably, Weinberger wouldn't talk about the hijacking crisis.

"I have no comment, except to say that Sol Linowitz has written a very good book."

Egyptian Ambassador Abdel Raouf Reedy would talk about it.

"We have condemned very strongly this act and we are doing our very best so that this can be concluded in a peaceful way. Luckily, many of the people got off the ship in Egypt, so many have been saved from this ordeal. We are taking good care of them. We will do whatever we can to help."

Lebanese Ambassador Abdallah Bouhabib was willing to talk, too.

"It seems that we're going from one disaster to another," he said. "I was pretty happy the ship did not come to Lebanon. It's not the same thing as a plane. You have to let that land, but a ship has enough fuel and food to stay at sea."

He said that the burden, like it or not, falls on the American leader. "President Reagan is president of the United States, but he is also the president of the free world, and it gives him the responsiblity of trying to solve the problems of the Middle East."