A Labour win will be a function of Blair's leadership and transformation of a party that it had been possible to doubt would ever win an election again. No leader has ever, at least in opposition, put his or her personal stamp on a party in the way he has. The question now is, can he run the country as firmly and distinctively?
This will depend on many things, among them the Cabinet he appoints immediately, how he can make the machinery of government work for him, and his own will for change and radicalism.
The Cabinet first. In theory, at least, Blair faces one constraint that would have appalled Attlee or Wilson: a crazy party rule which prescribes that the elected members of the Shadow Cabinet are appointed to the Cabinet. Crazy, because even when it was introduced during the high tide of Bennism in the early 1980s the Shadow Cabinet had only 12 members, leaving any prime minister the absolute right to choose over half his Cabinet. Now the elected members, plus all the ex-officio posts, including Leader and Deputy Leader, come to 27, and there are only 22 paid Cabinet posts. So something will have to give. Shadow Cabinet members will all be offered posts but it just isn't credible to assume they will all be in the Cabinet.
If there is a victory, Gordon Brown (Chancellor), Robin Cook (Foreign Office) and John Prescott (probably Environment and Transport as well as Deputy Prime Minister) are likely to be appointed tomorrow. Prescott has won massive brownie points for loyalty and energy in the election campaign, so the foregoing are shaping up like a possible "Big Four" of a Labour government.
Jack Straw will be confirmed as Home Secretary; David Blunkett will go to Education. Margaret Beckett, now indisputably a big player, will probably also be confirmed at Trade and Industry. Mo Mowlam is set for Northern Ireland
Beyond that it isn't easy to be certain: Alistair Darling, a campaign star and an unelected member of the Shadow Cabinet, looks likely be in the Cabinet. Donald Dewar could well become Scottish Secretary, charged with the massive task of seeing through the Devolution Bill, with the present incumbent, George Robertson, a candidate for Defence. Despite reports to the contrary, Clare Short may be safe with Cabinet responsibility for international development.
The Welshman Paul Murphy is heavily tipped for the Minister of State role currently taken in the political Northern Ireland talks. Peter Mandelson has delivered what looks - pending a result - like a hugely successful election campaign. But he won't be in the Cabinet, and won't be a ministerial "chief of staff". He will be a Minister of State - possibly under Cook, or elsewhere. The one certainty is that there will be no ideological bloodbath.
So how does Blair impose himself, and a collective strategy, on a government full of potentially warring ministers fighting turf wars? Semi-institutionalisation of an inner group drawn from among the Friday appointees would help. There might be areas they would find it difficult to agree; but once they had, it wouldn't be difficult to impose such an agreement on the rest of the Cabinet. Also, giving Blair's mentor, the Lord Chancellor, Lord Irvine, chairmanship of key Cabinet committees would ensure that a deeply trusted lieutenant was there to enforce the Prime Minister's will.
But ministers are only part of the story. Expect muffled squeals from the Civil Service when Jonathan Powell is confirmed as principal private secretary to the Prime Minister, replacing Alex Allan, who is likely to depart pretty swiftly for Australia as High Commissioner. Like Alastair Campbell, who will be the PM's press secretary, Powell will be coming in as a political appointee.
But private secretaries, unlike press secretaries have always previously come from inside the Civil Service. (William Clark, Macmillan's press secretary, and Joe Haines, who worked for Harold Wilson, both came from outside the Civil Service.) And this is a key job: Powell will be an unrivalled gatekeeper to the PM. His big brother, Charles, wielded huge influence on Margaret Thatcher's behalf, and he was technically only the No 2. However, the squeals may be quite short-lived. Powell is a civil servant rather than a politico by trade, and worked in the British Embassy in Washington when he was recruited by Blair. And there is nothing in writing to stop this happening.
Blair's view is that the quality, energy and trustworthiness of the people around him is more important than the machinery itself. Nevertheless, there has been one strong hint of a possible change.
The book The Blair Revolution, which Mandelson published last year with Roger Liddle, drew attention first to the need for the Treasury to have a broader role "than merely carving up public expenditure". Which under Brown it will certainly have. It also drew attention to the fact that while No 10 - "a town house rather than a stately home" - could only accommodate a small staff, through the green baize door is the Cabinet Office, which he implied should be more at the disposal of the Prime Minister. "The Cabinet Office should be more akin to the department of the Prime Minister and Cabinet ... acting more in future like a policy-making permanent secretary than as a business manager and minute-taker."
Sir Robin Butler - who irritated Blair's office by an over- zealous briefing this week on the mechanics of a government handover - is due for retirement as Cabinet Secretary by next year. When he is replaced - Andrew Turnbull at the Department of Environment is one of several possible candidates - the role of the Cabinet Office could be changed.
Even strong prime ministers find it difficult from time to time to impose their will on government. In his book on the British constitution, Ferdinand Mount, who was head of Margaret Thatcher's Policy Unit in the early 1980s, complains that it was an uphill struggle even for her. But Blair hasn't come this far to let his project be dissipated in Whitehall backbiting.
It looks as if the electorate has been utterly unimpressed by complaints about New Labour's lack of government experience. Perhaps, after all, if Blair had been born a Labour insider he wouldn't have even attempted what he has succeeded in doing to the party. His will isn't exactly in doubt. Attlee was a long-time member of the wartime political establishment when he became prime minister; Wilson had been a civil servant as well as a Cabinet minister. It may be a more positive advantage than anyone expects for Blair to have been neither.