As dead rats go, this one was enormous. But the Greens have managed to swallow it, and its members are now likely to make a meal of it.
They'll be bitterly unhappy that their MPs are supporting the waka-jumping law, which prevents an MP from quitting a party but staying on in Parliament as an independent.
Critics of the law, and the Greens have been at the forefront of it until now, see it as undemocratic. Former firebrand MP Sue Bradford says the current crop are dishonourable and should be thinking of how the party came into Parliament in the first place.
If the law had been around in 1999, former co-leaders Rod Donald and Jeanette Fitzsimons wouldn't have been able to leave the Alliance, and the Greens' journey into Parliament would have been stillborn.
Greens co-leader Marama Davidson put out a statement about their changed position on the bill saying they're supporting it "because the confidence and supply agreement holds us to it".
That's simply not true. There's no mention of it in the agreement, so her explanation's more of an excuse than reality.
Without their support, the bill would fail.
Davidson says their supporters may not like it but she's confident they'll come around after they see the gains they make in Government.
Yeah well, the 440ha that have just been set aside as a conservation park in the Mackenzie Basin for native grasshoppers, who don't like grass or hopping, is bound to placate them.
It's true the bill forces MPs to blindly follow a party's dictates, even if they change after an election, and that frequently happens as coalition governments are formed.
Parliament's history is littered with defecting MPs but rarely have they lasted beyond the next election.
This bill's Winston Peters' baby and if you need proof of who wields the power in this Government, this is it.
The fact that Justice Minister Andrew Little's fronting it, even though he's no great supporter of it either, is proof enough.
In its 25-year history New Zealand First has suffered more than most when it comes to defecting MPs. The last one was Brendan Horan who hung around like a bad smell, frequently getting up Peters' nose.
Peters forcefully argues the bill's in fact democratic in that is preserves the proportionality of Parliament that the voters would expect when they go into the ballot box and vote for a party.
But it also gives the party the right to expel electorate MPs who refuse to toe the party line.
That's probably why the global Inter Parliamentary Union sees laws like this one having the ability to create political party dictatorships.