If great theatre is the suspension of disbelief, then the play to see has been in Madison Square Garden this week. Normally, a party convention has all the spontaneity of the Eurovision Song Contest. Then along comes that figure in the trademark white shirt and plain midnight blue suit - and for a moment pigs can fly and men can walk on water.
On Wednesday night he did it again. To tell the truth, the substance of Mario Cuomo's nominating address for Bill Clinton wasn't really new. The themes, even many of the lines, have cropped up regularly in orations past. There was even a reference to the 'two cities' metaphor that brought the house down when he did the keynote in San Francisco, back in 1984. The genius of Mario Cuomo, though, is that he makes you think he's handing you the tablets from the Mount in person.
And then there's always the tantalising sub-plot. For the last eight years Mr Cuomo has been the unfulfilled Democratic dream, the man who could thrill the party, but for reasons known only to him refused to run for President himself. Would there be a hint of regret - or better still a coded message, 'Forget Bill - I, Mario, am your true leader'?
And after all, wasn't Mr Cuomo supposed to be the keeper of the party's liberal conscience, the immigrant's child who had risen to be chief executive of the glorious Empire State, who not so long ago was so dismissive of that smooth young moderate Governor from hillbilly-land in Arkansas?
And wasn't it only this year that he was castigating Mr Clinton for 'a slur on all the races' after those tapes which purportedly had Young Bill concurring with Gennifer Flowers that Mr Cuomo 'sure sounded' like a Mafioso? Not so, however. When the great moment came, Mario did Bill proud, and then some.
There was the soaring oratory, the grief at the fate of 'young people growing up with the sound of gunfire before they've heard an orchestra', and the castigation of President Bush for his politics of 'decline, decay and deceit'.
As an orator Mr Cuomo is without peer. The eyes may be pouchy, the mouth seemingly made of india rubber, the visage wistful, even lugubrious. But almost alone, he understands that a speech is more than shouting. He changes the pace, the volume and the emphasis. On Wednesday he was by turns sarcastic, alliterative and erudite, even bursting into Latin at one point, not the standard mode of expression at Democratic conventions.
But for a party so untypically hungering for unity, what mattered was his praise for Bill Clinton. Some had predicted that the nominee's name would barely feature. In the event, the 'C-word' came up 28 times in a speech of 27 minutes: 'Bill Clinton has always been driven by the desire to lift himself above his own immediate concerns: to give himself to something larger than himself.' No candidate could have sought a more compelling presentation.
When it was over they wept: and some did wonder, should not this have been the man giving the acceptance speech last night? But Mario Cuomo seemed at peace with the realisation, that at 60, almost certainly, he will never now be President - assuming he ever wanted the job in the first place.
For Mario Cuomo, what next? Mr Clinton has suggested that he would make an excellent Supreme Court justice, but that would be a waste, and for Democrats a deprivation. How else, every four years, will they so fiercely believe that this time, the game is theirs?