Tony Blair's dramatic intervention  in the centenary edition  of the New Statesman (180 pages, out now) leads several of today's papers (the Independent  and the Times  have splashed on it), with some of the former prime minister's key allies taking the opportunity to air their own concerns about the party's direction under Ed Miliband. The increasingly outspoken Peter Mandelson tells the Independent : "Tony is saying what he has always thought – that the old dividing lines between the uncaring Conservative cuts and Labour spending has got to be redrawn for new times.
"I suspect the two Eds realise this. Their call for One Nation is the right starting point, but there are major structural challenges and choices facing Britain and Labour must consider the difficult changes and reforms needed to address them."
Alan Milburn, Blair's former health secretary, adds: "The closer the election comes, people will stop asking Labour what it is against. They will want to know what Labour is for and what, if elected, it would do. Tony Blair is right to argue that the sooner that process begins in earnest, the better."
One suspects that Miliband, who wasted no time in shrugging off  Blair's warning not to "tack left on tax and spending", will be unfazed by their words. Both Mandelson and Milburn are no longer MPs, of course, and have little sway over today's Parliamentary Labour Party. But Blair's intervention and the response to it offers a preview of bigger battles to come. It's often said that Labour is more united now than at any point in recent history but this ignores the fact that there's been little to be disunited about.
Miliband's "blank sheet of paper" is gradually being filled but the Labour leader has chosen to postpone almost all policy decisions until 2014-15. Even when he proposes a new measure such as the reinstatement of the 10p tax rate, or the introduction of a "mansion tax", Miliband is careful to emphasise that these are examples of what Labour would be doing were it in power now, not manifesto commitments. The same applies to the party's five point plan  for jobs and growth, the 50p tax rate, benefits uprating and just about every policy area Miliband has touched on since becoming leader.
But at some point before the election, he will need to decide where he really stands. Will Labour, for instance, pledge to stick to  the coalition's spending limits for the early years of the new parliament (as Labour did with the Tories' in 1997) our outline its own alternative plan? What will the balance of tax rises to spending cuts be? Will he propose cuts to the welfare budget or allow the burden to fall entirely on public services? Will he pledge to keep Michael Gove's "free schools"? How far will he go in reversing the coalition's NHS reforms? Will he retain the £26,000 benefit cap?
Liberated from office, Blair enjoys the luxury of posing questions without answering them (although NS editor Jason Cowley has a go in today's Times ) but Miliband does not. And once he begins to set out his stall, Labour unity could quickly begin to fray. Recall the tumult that followed Ed Balls's declaration of support for the public sector pay freeze and Labour's decision to abstain on the workfare bill  (a move that prompted a rebellion by 44 backbenchers). As one Labour MP recently told me, a pledge to make further cuts to public spending (as the party will surely do) would make such rows "look like a tea party". For this reason, among others, David Cameron and George Osborne will continue to appear unreasonably cheerful. Most of their tough decisions are behind them; Labour’s are all still to come.