Political uncertainty is dissidents' best friend
We are now looking at new political negotiations and there is no great optimism about their success. But the cost of failure is very high - higher than before.
Take Sinn Fein. Until a couple of weeks ago they were presumed to be the ones who might walk from the Executive without more money on welfare reform. DUP backroom calculations were all about whether they wanted to or could be brought to a compromise.
Now, after the McGuigan murder and the police reaction, it is difficult for Sinn Fein to leave. Instead, the murder provides leverage against them. Collapsing the institutions in the wake of a murder would look guilty and would play badly in next year's elections south of the border.
Already, Irish Foreign Minister Charlie Flanagan has urged the parties here to avoid "car crash politics". He said that blanket denials by Sinn Fein of the existence of the IRA were unhelpful and he also put the onus on the republican party to provide reassurance and information.
When you are explaining, you are losing. The longer Sinn Fein prevaricates and the more denials it issues, the more mud will stick. The challenge is to get out from under the accusations.
Peter Robinson is both tough and astute - he will not miss these points of influence when he meets the Prime Minister David Cameron today.
Shortly after the McGuigan murder, he remarked on the "importance to politicians of getting issues dealt with through the political process and how easy it is to slip back when there is a political void".
He said that "there are always people who will fill that void, so it is up to politicians to up their game to ensure the political process has primacy and we don't give way to the people of violence".
He is right. If there is a long period of suspension or uncertainty, the dissidents will inevitably try to destabilise the situation through violence, if possible. Giving them that opportunity would be politically irresponsible.
If things do go badly it will be Sinn Fein and the DUP who take the blame, just as they will get the credit if things go well.
In this situation, there is something to be said for Mr Nesbitt and his party leaving the Executive - it looked like the UUP were clinging to it before. It takes them out of the firing line for decisions they can't really influence and cuts they didn't make. As Mr Nesbitt pointed out, they were frequently ignored and insulted, just like the SDLP and Alliance.
Being such a minority in government makes it hard for them to influence decisions. Mr Nesbitt is saying that if we want an all-party coalition, that will have to change and everyone will have to be treated with respect.
The alternative is to do what most other administrations do and fund an opposition.
That is a decision for the DUP and Sinn Fein to take in negotiations with the Irish and British governments.