Since Ed Miliband's election as Labour leader in his 2010, Tony Blair has sought to avoid explicitly referring to his obvious political differences with the man who sounded the death knell for New Labour.
But interviewed on the Today programme this morning on last week's Syria vote, he remarked frankly: "I wrote before the vote that I thought we had to support action in Syria and I said after the vote that I was disappointed by it. So this is something where I just have to disagree with the leadership of the party". What is significant is that he chose to blame Miliband, rather than Tory backbenchers or David Cameron, for the defeat, the first time he has openly taken issue with one of the Labour leader's stances.
Blair made it clear that he believed Miliband behaved irresponsibly by not supporting the government's motion last week. "Not to act, I think, is dangerous because you're sending a signal that such a use of chemical weapons can take place without the international community having a robust and proper response," he said. He warned that while military action could be "long and bloody and difficult and expensive", inaction would be "long and bloody and difficult and expensive and worse".
But while Cameron is also trying to frame Miliband as the guilty party, declaring at PMQs this week: "I don't think it was necessary to divide the House on a vote that could have led to a vote but he took the decision that it was", it's hard to think of a less helpful ally for him than Blair.
Every time that Blair champions intervention, it inclines many Tories to do the reverse. For Miliband, conversely, the former PM's criticism is political gold. It validates his claim to have "turned the page" on New Labour and helps to shore up the support of the key group of 2010 Lib Dem voters (who will determine the outcome in 2015), who abandoned Labour in protest at Iraq. As one tweeter wrote shortly after the interview, "I don't feel very inspired by Miliband at best of times, but the moment Blair starts criticising him, I go all protective and sympathetic."
Since last week's defeat, to the frustration of many Lib Dems, Miliband has framed himself as the man who prevented a "rush to war", as the antithesis of 2003-era Blair. In that task, nothing could be more helpful than the damning judgement of the man himself.
Update: Blair's once impeccably loyal deputy has rowed in behind Miliband.
I've always respected Tony Blair but he's wrong on Syria and Ed is right. Tony seems to have become a champion for regime change
— John Prescott (@johnprescott) September 6, 2013