Illustration: Andrew Dyson Cash finally admitted this after a day of fiercely denying her staff had any involvement. And with that the government's attempt to render this substantially more than a politically driven exhibition came crashing down. The trouble here is not the AFP, whose independence is not in question (Bill Shorten's description of the police as Malcolm Turnbull's "plaything" is hopelessly overblown). No, the trouble is with everything else around it. That the initial complaint came from the government itself, and was directed at the leader of its main political rival makes this an instantly political act. Then add the fact that the ROC, on whose behalf the AFP was acting, is a creature of the trade unions royal commission – a process whose entire being had clear political overtones. But it's also the fact that the suspected wrongdoing here was already examined in the royal commission, and seems so relatively banal. At issue is a $100,000 donation to a like-minded political activist group. When you consider that unions are political beasts that frequently donate to fellow travellers – not least political candidates – the donation seems utterly unremarkable.

Illustration: Simon Letch Sure, it would be illegitimate if not properly authorised by the union's executive. And perhaps one day we'll learn that it wasn't. But the problem for the government from the beginning is that it seems an entirely plausible thing for the executive to have decided, leaving it to fire up over missing paperwork and the like. ACTU secretary Sally McManus and and the AWU's Daniel Walton speak to the media after AFP raided the Spencer Street offices of the AWU. Credit:Chris Hopkins That's not to say such decisions should be above the law. But it is to say that if there's wrongdoing here, it doesn't quite seem to match the muscular imagery of the raid – imagery at least one Liberal Party staffer was keen to ensure would be broadcast to the world. And imagery that allows Malcolm Turnbull to intone gravely: "Bill Shorten has questions to answer."

Questions to answer. What a phrase that has turned out to be in Australian politics. You might remember the last time it was invoked: when Tony Abbott was hounding Julia Gillard over her dealings with the AWU back in the 1990s. Federal Police officers enter the AWU headquarters. Credit:Chris Hopkins You might remember how George Brandis took to parliament to label Gillard a criminal. You might remember that time Gillard held a press conference to answer every question journalists had until they had run out, in the hope that would put the issue to rest, and how it didn't. What you mightn't remember is what specific allegations were being made against Gillard. And that's because there weren't any. Who knows? Maybe this case will be different. But if it's not, the government faces some dangerous imagery of its own – namely of the repeated use of institutions to pursue political opponents. Embattled: Employment Minister Michaelia Cash. Credit:Andrew Meares

It is surely not mere happenstance that when it pursues a matter of union corruption it so frequently involves historic cases that involve a Labor leader. It is surely not a coincidence that two of its three royal commissions have been into Kevin Rudd's home-insulation program and then trade unions, while it stoically resists calls for one trained on the banks. It is one thing looking for political advantages where you can, seeking to frame your opponents in damaging ways and prosecuting a sustained line of attack. But it's quite another to weaponise important institutions for the task. These are things that should have an esteem well beyond the reach of partisan warfare. They are meant to stand when the political cycle of the moment has long receded. They are meant to be touchstones of national learning, cited for years to come. They are meant to build the legacy of a government, rather than its political strategy. Forget that and soon enough even the strategy doesn't work. The trade union royal commission gave the Coalition nothing in the way of political momentum. Shorten emerged relatively unscathed, as did Labor's poll lead.

Loading Political theatre only works where the audience suspends its disbelief and submits to the narrative on offer. That won't happen when the script is obvious and the characters are overdrawn. In that case, the more you see that story, the less compelling it seems to get. Waleed Aly is a Fairfax Media columnist and a presenter on The Project.