Two central truths dominate the result of the general election. The first is that Labour has won its third consecutive clear-cut victory for the first time in its life. For this, Tony Blair deserves much of the credit. The second is that Labour's share of the vote has fallen sharply since 2001. For this, Tony Blair deserves much of the blame.
Many readers will find one of those propositions far more acceptable than the other. However, it is in the interaction of these two truths that the outcome of the election needs to be understood.
Before Blair, Labour had won big-majority victories only twice: in 1945 and 1966. Both times, the following election produced decisive swings to the Conservatives: in 1950, Labour survived with a majority of just five, and lost power the following year. In 1970, the Tories gained 77 seats and Edward Heath became prime minister. Set against that background, Blair's record is remarkable.
However, if one considers Labour's ability to win votes, as distinct from parliamentary seats, a different picture emerges. With 36 per cent of the total vote, Labour has retained power with the smallest share ever achieved by any party winning an overall Commons majority. It broke a record previously set by Harold Wilson's Labour Party in October 1974. Then Labour won just over 40 per cent - and had a majority of just three.
Indeed, Labour's share of the total vote is not much above the 35.2 per cent it obtained in 1992 under Neil Kinnock. Set in the context of the 16 general elections since the Second World War, Labour's share this time is the fourth worst. It is lower than in the elections Labour lost in 1951, 1955, 1959, 1970 and 1979.
Iraq is the main reason for the swing from Labour to the Liberal Democrats. It mattered to only a minority of voters: YouGov's election-day poll for Sky News found that just 16 per cent regarded it as one of the two or three main issues determining their vote. But for many of that 16 per cent, Iraq was the decisive issue. Almost one in three Lib Dem voters told YouGov they would have stayed with Labour had it not been for Iraq - enough to have given Blair another victory on the scale of 1997 or 2001.
Put another way, Labour underpolled its natural vote. When people are asked which party they "generally" identify with - as distinct from how they were voting this month - Labour has a stable 44-32 per cent lead over the Tories, with the Lib Dems on 15 per cent. Yet again, Blair plays a double-edged role: he can claim the credit for winning over much of middle Britain and establishing a 12-point lead in party identification; but in this election he has also squandered part of the capital he has built up. One of Gordon Brown's challenges in due course will be to persuade the lost voters who still think of themselves as generally Labour to vote once more for the party.
The Conservatives face a different problem. They did poll their natural strength. Their challenge is not to persuade more natural Tories to return "home", but to make far more people identify with the Tories in the first place. For the past eight years, the Conservatives have been bumping up against a political "glass ceiling" - polling almost all of the one in three voters who still regard themselves as Tories, but hardly anyone else. That is why their vote share has been much the same at each of the past three elections. Until and unless the Tories change significantly, they stand little chance of returning to power.
As for the Liberal Democrats, the future looks highly frustrating. They gained both votes and seats, but not enough votes in the right places to secure the 70 seats that had become their unofficial target for this campaign.
As long as the present voting system lasts, the Lib Dems have two routes to the big time. One is to hold the balance of power and then use their bargaining position to help create a coalition, or at least secure electoral reform. The other route is to replace the Tories as Britain's main alternative to Labour.
The trouble is that the first route requires a significant Tory recovery, of which there is currently no sign. The trouble with the second is that it requires Tory disintegration - which is possible but by no means certain. The danger for the Lib Dems is that the Tories will remain too weak to recover, but too strong to implode. In that case, the Lib Dems will continue to find their ambitions thwarted.
Peter Kellner is chairman of YouGov