Like a Latin American politician whose party has been perceived in the past as too suspiciously left-wing by America's censorious opinion-makers, but which has suddenly been confronted with the real possibility of power, the Labour leader has turned pragmatic, judging it wise to mould his rhetoric to conventional US tastes.
He seemed to be begging for approval. Not so much the leader-in-waiting of a nation with which America is supposed to share a special historical partnership, more the reformed Nicaraguan radical pleading for investment money from Uncle Sam.
Whether Mr Blair was addressing Wall Street at lunch or Middle America on breakfast TV, the message was always the same: time has shown that you were right and we were wrong, that, yes, the time-honoured American orthodoxies do after all offer the best recipe for happiness and prosperity.
Thus, he assured his audiences, New Labour would not punish the people at the top; he would cut taxes; he would not roll back Thatcherite legislation and restore the unions to pre-eminence. "We used to be far too dominated by interest groups and pressure groups," he told ABC, sounding like a repentant revolutionary who has finally realised Marx was wrong.
In a slightly more sophisticated vein, as if taking his cue from the wordsmiths who shape the oratory of US election campaigns, he tossed his audiences some reassuringly familiar sound bites. He was "tough on crime"; he worried about "declining values".
"New Labour is a party of the centre ground," he declared. "New Labour is back in the mainstream." "New Labour is reunited with the modern world" - meaning with America, meaning forgive us our past misdeeds, oh mighty ones, and love us, take us back into your warm embrace.
If he didn't quite pull off the performance when he tried to sound like an American politician on the stump, it was because, rather charmingly, he lacked the customary gloss of cynicism, the carefully-honed gravitas. You had a sense that he was running, not for the leadership of one of the world's most venerable nations, but for the presidency of a student body.
Halfway through a dinner in his honour on Thursday at the residence of the British ambassador in Washington, he left his table to hear the result of the Staffordshire by-election. He returned, and for the rest of the evening appeared unable to wipe from his face an expression of puppyish delight. The big boys were there - General Colin Powell sat at his table, Ben Bradlee and other eminences of American journalism sat nearby - and he'd shown them he was a big boy too.
The ambassador's after-dinner address would have come across as embarrassingly trite before a London audience but in the circumstances was probably appropriate, reinforcing as it did the image upper-class Americans find so pleasing of Britain as a land of well-bred toffs. We learned that the ambassador and Mr Blair had attended St John's, the wealthiest of the Oxford colleges; we learnt that St John's owned so much land you could walk all the way to Cambridge without leaving college property, but "Who would wish to do that?" Ha ha.
When "the next prime minister", as the American media call him, stood up to respond, it was to announce with breathless excitement that his party had won in Staffordshire South-East, that there had been a swing of 22 per cent! Mr Blair paused for applause, and Gen Powell, who displayed less enthusiasm on learning he had won the Gulf War, politely patted his hands together with the rest of the bewildered guests. (Staffordshire who?)
After Mr Blair's speech the guests adjourned for brandy and port. "He's so young!" they whispered. "I've got a son that's four years older, for God's sake!" "He's 43 you say? He looks so boyish!" "He's so sweet and earnest!"
They were too courteous to say it, but what they meant was: there's no way a kid like this could become president of the United States.
Leading article, page 20