There has been a powerful shift in Stormont politics since the UUP and SDLP entered opposition, with the DUP and Sinn Fein welding themselves together in a bid to see off the new and somewhat unknown threat to their positions.
By contrast, the 28 Official Opposition MLAs have been sluggish, arguably providing less forensic scrutiny of the Executive than the solitary figure of Jim Allister.
But Saturday was the start of another shift in the Stormont dynamic: Just as the DUP and Sinn Fein have come together, so the UUP and SDLP are now openly coalescing against their common foes.
The image of Colum Eastwood being warmly received at an Ulster Unionist conference was visually powerful.
The UUP believe that Arlene Foster and Martin McGuinness simply could not appear like this at each other’s party conferences and are seeking to exploit that unique territory.
Although the DUP and Sinn Fein over the weekend were separately attempting to portray either Mr Nesbitt or Mr Eastwood as having gone constitutionally soft, they can only go so far with that line – ultimately it draws attention to their own increasingly firm alliance.
Having first shared power more than four decades ago, there is almost certainly more appetite among UUP and SDLP supporters for those parties to work closely together than there is among DUP and Sinn Fein supporters, few of whom pretend that they would work with the other if they had the choice.
Nevertheless, there is a danger for both the UUP and SDLP – partly because many voices heard in the media are demanding that they work as a single bloc – that over the next four years they blend together to become a less coherent version of the Alliance Party.
That almost certainly will please neither party’s supporters and could be electorally disastrous, especially if up against a DUP and Sinn Fein campaign centred around being the champion for unionists and nationalists respectively.
It may be that at some point in the future the majority of voters in Northern Ireland will decide to transfer between the DUP and Sinn Fein if they support the Executive or between the UUP and SDLP if they want them replaced with the Opposition.
But to date the electorate has consistently rewarded traditional parties who promise to champion their communal side against the interests of the ‘other side’.
But while most political rules will at some point be broken by a party sufficiently enterprising to gamble, there is a more fundamental problem for the nascent ‘middle ground’ alliance.
In an interview with the News Letter last week, Mr Nesbitt heavily indicated that he is looking to another electoral deal with the DUP in the next General Election.
It would be extraordinarily difficult to communicate why voters should vote DUP in one election to keep nationalists out, while in the next election urging voters to keep the DUP out – and perhaps even, if the UUP and SDLP urge their voters to transfer to each other, ask people to vote for nationalists to keep the DUP out.
The old politics of communal loyalty will put enormous – and, if the UUP enter an electoral alliance with the DUP, perhaps intolerable – strain on this bold new attempt by the Opposition.
It will be possible for the UUP to either advocate unionist unity or middle ground politics.
But to try to simultaneously ride both those horses is exceptionally ambitious.