With Labour more reliant on large one-off donations from unions, the Unite general secretary is in a stronger position to push for policy changes.
Labour suggests it will not impose the reform by changing the law with the Tories, but if the unions resist that may be the only option.
If the Labour leader is to be a consistent supporter of democracy and transparency, he cannot defend a system that allows unions to donate millions from their members without permission.
I joined the union as a fresh-faced student idealist but the camaraderie which I expected never materialised.
Tory MP Bob Neill's letter to the Metropolitan Police contains no evidence that the law may have been broken in seats other than Falkirk.
The growing strength of the Tory right and the anti-austerity left suggests our stable, predictable system of party politics may be coming to an end.
Desperate attempts to present Falkirk as part of a pattern of union abuse are as predictable as they are risible.
If the allegation that the union signed up members to Labour without their knowledge or consent is proven, it could be charged with fraud.
The Labour leader must use this moment to emancipate himself from the machine that won him the job in the first place.
The Unite general secretary hits back after Labour announces the end of the "union join" scheme and suspends Unite candidate Karie Murphy from the party.