When I asked Martin McGuinness about his relationship with Peter Robinson in May of last year he told me: "I have a very good working relationship with him. It is impossible to work with somebody over a four-year period and not develop a good working relationship. If you don't, it doesn't work."
That working relationship has visibly broken down – the two of them are seldom seen together, unless it is in America, and they are at loggerheads.
The question now is whether – and for how long – their joint Government can work.
There are good reasons to keep Stormont up and running, the principal of which is that turkeys should avoid voting for Christmas.
If the administration comes crashing down over issues like the Maze, marching and the past and the two governments have to be called in – as Gerry Adams hinted in the Dail – that will be a joint failure by the two biggest parties.
If the music stopped now the DUP might get the most blame, but that could change and both could suffer at some point.
Here, parties like the UUP, SDLP, Alliance and the rest would inevitably profit, and so might hardline loyalism and republican dissidents.
To extend the turkeys and Christmas analogy, there would be a feeding frenzy.
Sinn Fein is presenting its ability to govern with the DUP in the north as evidence that it would be a reliable partner in a Dail coalition, too. That was a major theme at the last ard fheis.
If Stormont crashes, Fianna Fail and Labour stand to benefit electorally at Sinn Fein's expense.
So it is in the best interest of the two parties to sit down and have a long, hard look at the situation. Both leaderships will be seen as lacking judgment if they cannot make this thing work.
The DUP knew it was entering government with a party that had been linked to the IRA and many of whose members were IRA veterans.
It is too late now – even a little childish – to start complaining when Sinn Fein members don't disown their IRA past.
The deal was that they should disarm and give up violence, not that they should, as Ian Paisley once demanded, "wear sackcloth and ashes".
Equally, Sinn Fein knew that it was getting into bed with anti-Good Friday Agreement unionists.
They had made a tactical decision to ditch the pro-Agreement ones, in the form of the UUP and David Trimble, because they felt that no deal would stick without the DUP.
Now it can't be too surprised when the DUP acts rudely and disrespectfully, especially with elections coming.
What needs to be restored, though, is trust. Whatever the rights and wrongs of the DUP's decision to pull the plug on the Maze, it went back on a deal that had been reached with Sinn Fein at the heart of government.
Mr Robinson needs to meet Mr McGuinnness here – not in China – to show him that business is continuing and that other deals will be honoured.
They need to appear together and they need to present a common front on some issues, otherwise they will both suffer.