The Arkansas Governor's acceptance speech which brought the proceedings in Madison Square Garden to a climax has been judged a triumph - not least because of its skilful blend of the promise of change and a stress on traditional middle-class values, tailored to recapture the lost votes of 'Reagan Democrats'. It was, even Mr Bush's Housing Secretary, Jack Kemp, acknowledged, a 'very fine speech'.
Now, however, Mr Clinton has to keep the bandwagon rolling. One poll yesterday gave him an astonishing 23-point lead. But as every Democrat grimly remembers, at the same moment four years ago, Michael Dukakis left the Atlanta convention with a scarcely less imposing advantage of 17 per cent - only to leave the campaign trail and surrender the initiative, as it turned out, for ever.
The Clinton camp will not make the same mistake. Less than 24 hours after apotheosis in Madison Square Garden, he had left New York along with his vice-presidential nominee, Al Gore, for an old-fashioned barnstorming bus tour to eight north-eastern and Midwestern states, to carry their message of generational change to workers and ordinary people.
But with the political landscape turned upside down by the stunning withdrawal of Mr Perot, the Republicans too are not waiting until their mid-August convention in Houston to begin their own chase to round up Perot defectors and concentrate their fire on a target now narrowed to one.
Vice-President Dan Quayle yesterday travelled to Florida to shore up Republican support in a key Southern state where Mr Perot had made deep inroads. The word on his lips too was 'change': but this time the sort he claims Mr Bush could bring about, given a change of guard on Capitol Hill. With Republican control of Congress, argued the Vice-President, 'George Bush will change America as he has changed the world'.
The Republicans' main assault, however, will be a familiar one. Yet again, they are out to portray a Democratic ticket as the same liberal mutton dressed up as moderate lamb. Mr Clinton will be presented as the youthful, untrustworthy heir of Mr McGovern, Mr Mondale and Mr Dukakis, at the wrong end of electoral landslides in 1972, 1984 and 1988.
The difference this time will be the legacy of Ross Perot. The man may be, as Stephen Hess of the Brookings Institution put it yesterday, 'forgotten in two months, destined to be a metaphor for a short-lived political fad'. But his millions of supporters, energised by the prospect of change, remain a force which could decide the outcome in November.
The immediate beneficiary of Mr Perot's bombshell decision not to run is probably Mr Bush, who can count on victories in states like Florida and Texas and other traditional Republican strongholds where the Dallas billionaire might have won outright, or handed victory to Mr Clinton.
Democrats believe, however, that the underlying dynamics favour them. The timing of his pull-out allowed both Mr Clinton and Mr Gore to appeal on Thursday evening, on prime-time network TV, for the allegiance of Perot supporters. 'Stay involved,' urged Mr Gore; they were, said Mr Clinton in his acceptance speech, 'an army of patriots for change. We say to them: join us'.
As things stand, that might just happen. A CNN/Gallup poll taken before Mr Clinton's address showed potential Perot voters favouring him over the President by a margin of three to two. Added to that must be Mr Perot's quasi-endorsement of Mr Clinton. A 'revitalised' Democratic Party was one of the reasons he had quit. The question is whether his cruelly disillusioned followers any longer believe a word that comes out of his mouth.
'It's like a sudden divorce,' said Joan Vinson-Stalling, the chief Perot organiser in Maryland, voicing the continuing bewilderment and disorientation of his supporters nationwide. 'We just don't know how to deal with it. But the movement goes on.'