No doubt, both Conservatives and Liberal Democrats, joined by a select band of Blairite survivors, would be rather chipper if the trade union chiefs currently making threatening noises about cutting Labour Party funding  turn out to really mean it.

But the real benefit could be much wider: if Labour loses a large chunk of its funding from trade unions bosses then it could unlock the long-running saga that political party funding reform.

Back in December I wrote:

The strong historical links between trade unions and the Labour Party means that any proposals which would curb the amount unions can give to Labour are fiercely opposed.

But Labour is not the permanent party of government.

Requiring union members to opt in explicitly to make donations and choose which party they wish their funds to go to would certainly hurt Labour relative to other parties. However, becoming the conduit of mass funding to all the main political parties (remember just how many trade unionists vote for parties other than Labour) would make other parties pay more attention to the concerns of trade union members. It may weaken support for Labour and reduce the role of trade union bosses, but it would strengthen the political influence of trade union members. Were it not for the weight of history, this move would make sense. As it is, it is very unlikely.

If Labour loses a large chunk of its trade union funding then the financial pain of political party funding reform would start looking rather small – especially as backing meaningful reform would let Ed Miliband push David Cameron hard on the sort of low donation cap that would block predominantly large Conservative donations.

Moreover, whilst party funding reform would strengthen the influence of individual trade union members, the one clear loser would be the senior trade union figures who currently hold the purse strings. And if they are gunning for Ed Miliband, is weakening their position really so unthinkable for him?

In fact, even if those senior trade unionists are bluffing, they are offering up to Ed Miliband the perfect opportunity to be tough (standing up to them), to be consensual (agreeing to the previous independently drawn up proposals for funding reform )and to be on the side of the many, not the few (getting the big money out of politics).

Will he take the opportunity?

* Mark Pack has written 101 Ways To Win An Election and produces a monthly newsletter about the Liberal Democrats.