"It is my rejection of... New Labour nostalgia that makes me the modernising candidate at this election," wrote Labour leadership candidate Ed Miliband in an essay for the Fabian Society in August 2010. At the time, the younger Miliband was the outsider, the underdog; brother David, the Blairite candidate, was the hot favourite.

But it was Mili-E, not Mili-D, who was crowned king of the Labour party the following month, in Manchester, after stressing, again and again, the need for "change" over "continuity". His campaign was based on moving on from 'New Labour', apologising for the invasion of Iraq.

So why is the Labour leader joining Tony Blair for a high-profile charity event at the Emirates Stadium this evening? Why has he allowed Blairites to brief that their hero is a close adviser and mentor to Miliband?

"It's a mistake," says a shadow cabinet minister, referring to this evening's event. "Tens of thousands of people have joined the party since Ed became leader. They'd either left [under Blair and Brown] or refused to join. Why demotivate them like this?"

One aide to Miliband tells me he has "serious concerns" about the meeting with Blair: the anti-war left consider TB to be a "warmonger" and "war criminal" while the Daily-Mail-reading right loathe the former PM, and his wife Cherie, as money-grubbing, perma-tanned frauds. So who does Miliband end up appealing to, or even appeasing, standing shoulder to shoulder with Blair this evening? He has, so far, avoided the Tory tag of "Son of Brown" - does he really need the tag of "Son of Blair"?

However, a former member of Blair's Cabinet says the event is a "no brainer" for the Labour leader: "By being seen with Tony, he unites the [Labour] party."

Hmm. I'm not sure a leader with a double-digit lead in the polls, a noticeable edge over the PM at PMQs and a series of astute judgement calls (including demanding the resignations of Rebekah Brooks and Bob Diamond) under his belt needs to worry about uniting his party. Success tends to breeds success - and hangers-on.

So while I understand what Blair gets out of the joint appearance at the Emirates Stadium, I'm not sure what Miliband gets out of it. Yes, the former premier won three consecutive general elections - the only Labour leader to do so! - but, as I wrote on the New Statesman blog back in March when TB staged his last 're-entry' into British politics, his legacy is suffused in myths and legends and so it is worth (re)considering these five key points:

1) In July 1994, Blair inherited a 13% poll lead over the Tories from the late John Smith; it was handed to him on a plate. Despite extending it to a massive 29 points in June 1995, on election day in May 1997, Labour beat the tired, divided, lacklustre, scandal-ridden Tories by - wait for it - just under 13 percentage points.

2) Labour lost four million votes on Blair's watch, between 1997 and 2005 (and another million on Brown's watch, in 2010). From the moment Blair walked through the black door of Number 10, the Labour vote share started to decline and the 'master' himself could do little to halt or reverse it in the subsequent general elections.

3) Blair won his three election victories, in an age of affluence, against John Major, William Hague and Michael Howard (who picked up the baton from Iain Duncan Smith). He never had to face a tough opponent - be it Ken Clarke, who the Tories crazily rejected again and again, or Blair's own 'heir', David Cameron.

4) Blair benefited from a voting system that is biased in favour of the Labour Party: in 2005, for example, TB secured a third term, with a healthy 66-seat majority, on just 35.2% of the vote (that is, one in five eligible British voters). Five years later, however, Cameron's Conservatives couldn't get a majority in the Commons despite winning 36.1% of the vote.

5) By the time Blair reluctantly left office, in the wake of a series of embarrassing scandals and unpopular wars, his sheen had worn off - the Tories' had a near-uninterrupted poll lead over Blair's Labour Party between December 2005 and Blair's resignation in May 2007. Unlike Blair, Ed Miliband inherited a Labour Party trailing the Tories in the polls in September 2010.

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