Two months after Bill Clinton's presidential victory in November 1992, Gordon Brown and Tony Blair flew to Washington to visit Democratic campaign advisers. It was a visit which was to have a dramatic effect on Blair. Three days after he returned, he first used the phrase "tough on crime and tough on the causes of crime". Suddenly he was a politician with mass appeal.

The phrase was supplied by Brown, but the thinking behind it was joint intellectual property, brought into focus by the Washington trip. One of the ways in which Clinton was "a different kind of Democrat" was that he was "tough on crime". In America, of course, toughness goes much further than in Britain. For one thing, it means unhesitating support for the death penalty. But Blair and Brown were interested in the broader political strategy of Clinton's "modernising" faction in the Democratic party.

Clinton's ideological power base was the Democratic Leadership Council, which he helped to set up in 1985. The DLC saw its task as forcing the party to come to terms with social change. It was called "reality therapy". For Paul Begala, Clinton's strategist and speechwriter, it was very simple: "We had to start with reality, which is that we'd lost so many of the previous elections, and I think Governor Clinton's greatest insight was, it wasn't the voters' fault, there was something wrong with the partythat we did need to change."

It was immediately clear to Blair and Brown that they and the "Clintonistas" were talking the same language.

The DLC's aim was to give the party a "populist" message, one that reflected the values of the majority in the country. This was why crime was important. The problem was that voters thought that Democrats were keen to excuse criminals from personal responsibility - exactly the same perception that British voters had of Labour. "The right has won public support through its willingness to emphasise moral accountability in the fight against crime - an accountability too many on the left felt uncomfortable in publicly espousing," wrote Ed Kilgore, a DLC policy analyst, in December 1992.

Kilgore urged the incoming Clinton administration to consider "tactics and strategies that not only work against crime and the conditions that breed it, but that restitch the fabric that holds our communities together".

Those words were an uncanny preview of the themes Blair was to develop throughout 1993 on his return from America. He had already seen the potential of a turn towards what could be called social moralism. That was why he had asked John Smith for the postof shadow Home Secretary.

The question of personal responsibility for crime was part of a larger theme in the Clinton campaign. It was expressed in forthright language by Paul Begala: "There had been a drift in the past toward a notion that the larger community owed the individual something, and yet there was no reciprocal obligation. That was wrong. It was destructive of the social order."

In America, these ideas were associated with a new school of political philosophy called "communitarianism".The ideas of American communitarians were not new. They had rediscovered the work of, among others, an obscure Scottish philosopher called John Macmurray, a Christian socialist whose work had, appropriately enough, inspired Blair at Oxford in the early Seventies. In the Clinton campaign, Blair suddenly saw how his long-standing left-wing convictions - formed at the same time as his Christian belief - could be turned into an aggressive political strategy.

The themes of Blair's argument were simple. First, society has a responsibility to give people the hope of a better life. Second, people have a responsibility to give something back to society and to obey its rules. And third, because mutual obligations originate in family responsibilities, the family must be strengthened.

The first part was standard Labour Party doctrine. The second part, personal responsibility, was entirely new to parts of the party. Blair's innovation was to go beyond the standard line to talk about being tough on crime, punishment, and even to hint atimposing obligations on the unemployed to take up "opportunities" offered to them. At the time those seeking more specifics from Blair were met with the exasperated response: "You don't understand - no one in the Labour Party has used the word `punishment' for years."

Tellingly, it was in the Sun that Blair chose to expound his new populism. In March 1993 he wrote: "It's a bargain - we give opportunity, we demand responsibility. There is no excuse for crime. None." In just six months, the stance and language had been transformed, from the old Labour apologia of his 1992 conference speech, when he said: "There is no excuse for crime. But ..." Now he seemed to echo the words of Margaret Thatcher when the Brixton riots burst upon a horrified middle England in 1981: "Nothing can excuse the violence."

Blair's attempt to "moralise politics" took a further step in the wake of the horrific murder which seemed to link crime with family breakdown - that of two-year-old James Bulger by two 10-year-olds. In a speech in Wellingborough on 19 February 1993, Blair described the disintegration of society in a moral language entirely alien to Labour politicians: "We cannot exist in a moral vacuum. If we do not learn and then teach the value of what is right and what is wrong, then the result is simply moral chaoswhich engulfs us all ... The importance of the notion of community is that it defines the relationship not only between us as individuals but between people and the society in which they live, one that is based on responsibilities as well as rights,

on obligations as well as entitlements. "

The third part of his argument - the need for "strong" families - was expressed by stealing a Conservative phrase: "It is parents who bring up kids, not governments" (The Sun article again). It was the right time to reclaim it. The wave of concern about youth crime meant that both the Labour Party and the country were receptive to a new message.

Blair was emboldened to use not just Conservative phrases, but to lay claim to some of the roots of Conservative philosophy - Edmund Burke's 18th-century notion that a nation is built up from "little platoons", starting with the family. In June 1993 Blair said: "It is largely from family discipline that social discipline and a sense of responsibility is learnt. A modern notion of society - where rights and responsibilities go together - requires responsibility to be nurtured. Out of a family grows the sense of community."

This speech, in Alloa, was an early instance of his promotion of the two-parent family: "All other things being equal, it is easier to do the difficult job of bringing up a child where there are two parents living happily together." He drew attention to the "fairly appalling" fact that 10 years after marriage breakdown, half of all fathers have lost contact with their children.

But - like Clinton's - Blair's "revolutionary" social moralism was not just about the issues of crime and the welfare state. For Clinton's advisers, what they called social conservatism meant identifying with the values of the majority. It was only by doing this, they argued, that the voters would trust Clinton on taxes. It helped, of course, that Clinton proposed to raise taxes only on those earning more than $200,000 a year - fewer than one in 100 American taxpayers - whereas Labour in 1992 intended to hit people earning £22,000 a year, or one taxpayer in six.

Clinton succeeded - temporarily - in making the Democrats the party of upward mobility for the electoral middle ground. Clinton called them "the forgotten middle class, who work hard and play by the rules". Blair now calls them "middle-income Britain" and says he wants to reward those "who work hard and do well".

The sting in the tail, of course, is that Clinton's administration started a slow slide into disarray almost from the day of his inauguration. Asked about the Democrats' defeat in the mid-term elections, Blair said last month: "You don't run on one basisand govern on another."

The trouble is that Clinton ran on two bases at once, and fell between both of them in office. His campaign appealed to traditional, liberal Democrats and at the same time persuaded conservative, middle-ground voters that he really was a "different kind of Democrat". But, in power, he was unable to deliver either the "New Democrat" goods - welfare reform - or the liberal goods - universal health care.

Blair's response is: "We have got to be quite clear about our priorities as New Labour, what we're going to do, what we're going to achieve, and how you deliver those specific objectives"

Judging by Labour's disarray over policy since the new year, that - as with so many Blairisms - is easier said than done.

The author's biography of Tony Blair will be published by Little Brown in September.