One of Tony Blair’s abiding gifts to political discourse is the concept of the “Clause Four Moment” – now shorthand for those crunch times when political leaders put decisive stamps on their parties. In one of Blair’s earliest moves at the Labour helm, he forced through changes to a key element of the party’s constitution that outlined core aims, trimming out a sentence that apparently set full-scale nationalisation as a primary goal (although it has been interpreted in other ways). Since then, the phrase “Clause Four Moment” has become synonymous with attempts to redefine political identity to the electorate. One could argue that much of David Cameron’s time as opposition leader was spent trying to achieve a Conservative Clause Four Moment – albeit through recasting his relationship with huskies and hoodies rather than industrial ownership.

Until this week, Ed Miliband had dismissed the idea that he needed a Clause Four Moment of his own. In contrast to Blair, Miliband rejected the idea of defining his own political values by contrasting them against those traditionally associated with his party. Instead, he sought to reclaim some of the ideological baggage jettisoned during the Blair/Brown years and articulate how it provides answers to contemporary challenges. All of which makes this week’s speech outlining a plan to overhaul the Labour Party’s relationship with trade unions something of a surprise.

Miliband’s speech on Tuesday was not a pre-determined moment at which to signal a bold vision for a realignment of British politics – and was unlikely to have been delivered in the first place, had David Cameron not repeatedly shouted “Len McClusky” across the floor of the Commons last week. As such, the Conservatives could well use Miliband’s intervention as further evidence that he is weak, and unfit to lead either his party or the country.

However, a more generous interpretation may be that Miliband has emphatically seized the moment. As Barack Obama’s former Chief of Staff Rahm Emanuel once famously said, “You never want a good crisis to go to waste.” While the circumstances are probably not what he himself would have chosen, Miliband now has an opportunity to take on a vested interest closer to home than the press barons he has already been seen to challenge. In this light, Miliband’s call to restrict MPs’ earnings from outside Parliament could be an additional bit of smart politics – the next set of taunts about Labour’s financial dependency on the unions could be met by questions about how independent the higher-earning Conservatives are from their own paymasters.

Ed Miliband may not have felt it necessary to have a Clause Four Moment, and he may have been bounced into this one – but a show of strength in the face of adversity could work wonders for his prospects in 2015.