Feeling of deja vu over latest Stormont impasse
Peter Robinson had been hoping the UUP would support his party's call for the Assembly to be suspended for four weeks, perhaps six, to allow for talks. The fact that the UUP didn't shows the depth of the grudge match between the two former allies.
It is not so long ago since they were forming joint fronts on Orange parades and even fielding joint candidates in the Westminster elections. Mr Robinson used to invite Danny Kennedy, the UUP minister who officially leaves office at midnight tonight, to DUP group meetings and say the relationship was as good as with his own ministers.
That has all soured and it isn't a complete surprise to the DUP, though the timing caught them off guard. It was always on the cards that, given the right issue, the UUP might leave the Executive before the election.
Protesting at a murder with IRA involvement and Sinn Fein denials of the IRA's existence is just the sort of reason unionist voters tend to understand.
Unionist unity in a marginal seat is one thing but the position of the two parties is competitive. The UUP won two seats in the recent general election, one from Sinn Fein with the help of a unionist pact, the other from the DUP.
In this instance it is almost certainly a good idea to suspend the Assembly. It allows for concentrated, pressured negotiations without meetings of the Executive or Assembly intervening and some business can still be done.
There is no principled unionist objection to it. It is even the tactic that the UUP used when they were the biggest party and David Trimble was First Minisiter. Mr Trimble resigned twice as First Minister in rows over decommissioning. The Assembly itself was suspended for about five years between 2002 and 2007. If the UUP once did what they now criticise the DUP for doing, Peter Robinson also behaved like Mike Nesbitt when the roles were reversed.
Back in 2002, the DUP pulled out of Stormont following the discovery of an IRA spy ring, which ironically included the British agent Denis Donaldson, and Mr Robinson and Nigel Dodds quit the UUP-led Executive.
Mr Trimble was forced to collapse the Executive following a meeting with the Prime Minister. Will history repeat itself?
There is no doubt that Mr Nesbitt has struck a chord in the unionist community - but there is an awful lot riding on the Assembly. MPs such as Ian Paisley and Gregory Campbell have been the most outspoken about the need for strong action.
They are more militant than the 38 DUP MLAs and their staff, not to mention those who work in DUP offices across the country. Their jobs depend on the Assembly somehow getting through this crisis.
A four-week suspension with pay would be no problem, but if a collapse lasted years then the political class would begin to dissipate as people looked for work.
One estimate is that 400 jobs would be on the line and all parties are under similar financial pressures. A lot of Sinn Fein general finance depends on MLAs and other employees' salaries being handed in to the party in return for an allowance.
It is also a ticklish problem for David Cameron. If he allows the Assembly to collapse then the whole problem lands directly back on his lap at a time when he has bigger fish, such as the EU referendum, to fry.
On the other hand, he has to satisfy unionists that republicans are being held to account or Mr Robinson will be forced to quit. Mr Nesbitt's resignation strengthens Mr Robinson's hand on this score. The future of Northern Ireland is also at stake. At a time when devolution is spreading across the UK, failing to make it work puts a question mark over the region's viability.
The question of Irish unity, long faded from practical political discourse, would come back on the agenda if Northern Ireland seemed ungovernable. The British partnership with the Irish government would become even more important.
We would, in other words, be in uncharted waters with all our existing economic and communal problems but no local forum to deal with them.
Mr Nesbitt's decision to form an opposition may yet be a catalyst for change in the Assembly, but he and all the other party leaders still need to work together to get us through this impasse.
We need all the local party leaders at the talks prepared to reach agreement. The stakes are too high for posturing.