Almost every family has an embarrassing relative – the one who makes eyebrow-raising comments about Chinese gymnasts or once had to be carried out of Aunt Sylvia’s second wedding face down in the top tier of the sponge cake. Even the Middletons, who produced our preternaturally perfect future queen Kate, have one: Uncle Gary, once caught by the News of the World with drugs and ladies of the night in his Ibiza pad, La Maison de Bang Bang.

But that’s enough about a man with lounge-lizard dress sense and a deep tan who has been accused of trading on his personal connections. What I really want to talk about is Tony Blair.

Our former prime minister is the Labour Party’s embarrassing uncle: the rich one who slips you cash but you’d rather people didn’t know is related to you. This was made obvious earlier this month when Blair donated £106,000 to help candidates in 106 of Labour’s target seats. The structure of the donation felt like candidates were being forced to take a test on how they felt about Blairism. In the end, only a handful turned the money down; one of the few who did was a PPC who served in the Iraq war.

This is a decisive moment. All the indications are that the 2015 Labour intake will be more left-leaning than its predecessors – for example, a snapshot poll by CND found that three-quarters of them did not want to renew our commitment to Trident. So it is heartening that so many of them accepted Blair’s money. It suggests the party is finally coming to terms with the legacy of his premiership in a way that recognises the good as well as bemoans the bad.

To be fair, the left has always been more prone to self-flagellation. The ability to criticise your own side can even be an endear­ing trait, particularly when contrasted with the ridiculous over-veneration the right gives to its most divisive leaders. As Simon Heffer argued in these pages in January, some right-wingers call it heresy to mention Winston Churchill’s prejudices and pre-war failures. When Margaret Thatcher died, some newspapers practically patrolled the streets searching for anyone who didn’t look sad enough in order to berate them for their lack of patriotism. Somehow, I doubt the Guardian and Mirror will return the favour when Our Blessed Tony shuffles off this mortal coil. In fact, lefties will probably lead the effigy-burning.

This hypercritical streak has its downsides. In the 2010 Labour leadership election, Ed Miliband’s candidacy was undoubtedly helped by the simple fact that he was not in the Commons at the time of the Iraq war vote in 2003, unlike his brother, David. He is said to have opposed it ­privately at the time but that was a much less difficult decision to make from the safety of Harvard. He simply never faced the choice between party loyalty and conscience. As a result, Ed Miliband was free to reject the toxic legacy of the war, as car bombs scarred Baghdad and instability spread across the region. Because he didn’t have to “own” the decision to back the Iraq misadventure, he was free to present himself as a break with the past.

The trouble was, that rejection spread to encompass not just the Iraq war but all the good bits of New Labour. The party’s economic legacy is now defined just the way the Tories want it, by the financial crisis (as if the right would have regulated the banks much more strictly during the boom years) rather than by years of growth, lower poverty rates and higher living standards.

It would have helped, of course, if Blair had behaved differently on leaving office. Even his closest supporters must wish he had dis­appeared from sight and emerged only to show off his nauseating paintings of West Highland terriers, like George W Bush. Instead, there he was, looking harried in open-necked shirts in his role as the Quartet’s Middle East peace envoy. In terms of symbolic reminders of failure, this is like Gordon Brown leaving No 10 and going to work in H Samuel.

As a result, Labour kept feeling the need to distance itself from Blair, hobbling its ability to defend its record. For fear of someone – probably from its own side – shouting “Iraq!”, its politicians and activists have taken a voluntary vow of silence, preventing them from boasting about creating the national minimum wage and enshrining child poverty targets in law. They have been reluctant to mention successes in Kosovo, Northern Ireland or Sierra Leone, even in the same breath as condemning the failure in Iraq. It is now taken for granted how dramatically New Labour changed Britain’s centre of gravity by wrenching the Tory ­party leftwards on social issues such as gay relationships, racial equality and the promotion of women in public life.

As Zoe Williams observed in the Guardian last year: “Even to say that ‘other things happened during the Labour term besides a war many of us did not agree with’ is seen as disrespectful.” At its worst, this distancing strayed into an overt longing for the purity of opposition. If only the Tories had been in government! They never would have gone to war in Ira– sorry, what’s that? They voted for it, too?

I am not arguing that politics should be without morals, or that politicians should not be held to account for their mistakes. But Labour’s failure to come to terms with Blair’s legacy is a microcosm of the new perfectionism sweeping politics, where it feels morally purer to vote None of the Above rather than to risk getting it wrong. I worry that we don’t want politics to involve compromises, or hard choices, or human frailty.

Like any occasionally embarrassing relative, Uncle Tony still causes Labour twinges of shame. But it seems the party is finally ready to acknowledge that he has always been part of the family.