Mario M. Cuomo gave a little demonstration of the kind of campaign he might run, were he to decide to run for president. He will talk about the economy, about what happened to it, and make it sound like a rumba lesson. The sauce for the substance will be zest and humor, lots of allegro vivace, lots of body language, podium pounding and gesticulation with his large workman's hands.

His audience at the National Press Club yesterday rocked with laughter as he roared through his reflections on the dismal science. The New York governor was positively operatic in his recreation of what happened to the national budget. He imitated President Bush telling Congress it had to do the budget, imitated Senate Majority Leader George J. Mitchell (D-Maine) saying, "You gotta do the budget, this is it, this is the best thing you can do."

But, he said, "People called up and said" -- and here he did a Bronx cheer -- "and what happened? They did another budget."

This city is obsessed with the possibility of war and the desirability of starting one soon. At Christmas parties, people are screaming at each other about cowardice and war wimpiness and other unseasonal subjects. Cuomo bypassed all that, citing the economy as a "long-term national economic crisis that is as dangerous" as the situation in the Persian Gulf. He's a bit leery about foreign policy since he got burned for a West Coast speech about a compromise with Iraqi President Saddam Hussein.

He does not tailor his texts for television times. His oratory, in this era of sound bites, is more in the nature of a five-course banquet. He started out voicing eagerness to get to the question period but spoke so long he cut the question period in half.

He has found a metaphor that we may hear for a year or more. It's about the captain of a ship who is on a collision course with what he thinks is another ship. He keeps ordering it to change course. Finally, the voice of the blip on the radar screen speaks: "This is the lighthouse, you {change course}."

Bush is the captain of the ship, of course. Cuomo thinks he has done splendidly in the Middle East but has ignored disasters at home.

He will charge Bush with following the "economic fundamentalism of 65 years ago," instituted by Ronald Reagan, a president "whom we loved -- and believed."

The New York state budget is a billion dollars short. But there is a reason: "I am a governor who has been on the front lines dealing with a national recession." Washington is a place where they hate "to make the hard decisions." He has made them, he insisted -- he has cut one of every eight dollars in his own budget.

He will conduct a positive campaign. He thinks it's the individual's ideas rather than the individual that matters. He is not sure, however, that he was right to tell 1988 Democratic nominee Michael S. Dukakis, 15 minutes before the second presidential debate "you are positive . . . play your own game . . . you are naturally constructive."

It is hard to imagine that Cuomo, who is as assertive as he is thin-skinned, would follow Dukakis's example and let Bush climb all over him. Cuomo would not suffer in silence while Bush trashed New York, the way he trashed Dukakis's Massachusetts.

Cuomo will argue with a reporter for hours over a single sentence in a story. To think that a charge from Bush would go unanswered is not realistic, nor is imagining him letting Bush get away with using the "L word" or the "T word" or any of 1988's other silly circumlocutions.

He gave some idea how he would handle any mud hurled by White House campaign operatives. He would laugh at them as the missiles, the '92 equivalents of flags and furloughs, came hurtling over. He told of the reaction of the president's men to each potential Democratic candidate, including himself: "He's got a name Mario Cuomo. Everybody thinks he's a bodyguard in 'The Godfather.' "

He even has an ingenious explanation of why he had such a relatively poor showing in his last election, a mere 53 percent of the vote. Without mentioning his disappointment specifically, he wrapped it in an excuse he gave for the even worse showing, 51 percent, of Sen. Bill Bradley (D-N.J.), another presidential possibility. Middle-class people in New Jersey, Cuomo said, were saying " 'Please pay attention to us. Please.' Sometimes children will even do naughty things to get your attention, like vote against you."

Soft on crime? No one has been more niggardly with clemency for convicted criminals. Jean Harris, the former headmistress of Madeira School, who killed her lover and is spending her ninth year in prison, is the subject of an intense clemency campaign by prominent writers and thinkers. The governor will not budge. Asked at the lunch, he said he has "more and more respect for the law."