Ever since the Coalition government was formed a year ago with the intention of governing for five years, a single overarching question has hung over its ultimate long-term survival.
It is what would happen if and when membership of the Coalition became a political liability for one or other of its partners.
Well, to no-one’s great surprise, least of all mine, that question has now assumed a certain degree of urgency.
The Liberal Democrats’ calamitous performance in Thursday’s council elections will surely lead to fresh unease among party members over just how long they can go on being David Cameron’s fall-guys.
Even leaving aside the result of the referendum on the voting system, still to be officially announced as this column goes to press, it was a bad, bad night for Nick Clegg and his party.
The loss of Newcastle City Council to Labour after seven years was not the half of it.
That result merely restores what has always seemed to be the natural order of politics in the city after a Lib Dem interregnum which was initially a consequence of the post-Iraq backlash against Tony Blair.
More damaging by far was the slump to 15pc of the national share of the vote, some 22pc behind their Coalition partners whose support held steady from last year’s election.
There will doubtless be some bemused Lib Dem activists who wonder why they, rather than the Conservatives, are currently taking the political hit for the government’s spending cutbacks.
There are several reasons. For starters, while those who voted Tory last May were by and large supportive of the cuts, that is not necessarily true of Lib Dem voters.
It stands to reason therefore that Conservative support is holding up better in the wake of the cuts than that of a party whose supporters were more in sympathy with Labour’s more gradualist approach to deficit reduction.
More specifically, the cuts are disproportionately affecting many of the areas, particularly in the North, where the Lib Dems were doing quite well until Thursday night.
But the biggest and most fundamental reason for the Lib Dem collapse is that the decision to enter the Coalition, and the way Mr Clegg had handled the relationship with the Tories, has left many voters confused about the party and what it stands for.
Ever since Paddy Ashdown abandoned “equidistance” between the two main parties in favour of a closer relationship with Labour, it has been perceived as a centre-left party – a perception strengthened by its opposition to the war in Iraq.
In the light of this, Mr Clegg should perhaps have taken more care to appear as a reluctant participant in the Coalition, emphasising that he was joining it purely in the interest of providing stable government rather than out of any sense of policy convergence.
But by making it appear instead like he and ‘Dave’ were enjoying some kind of ideological love-in, he has alienated that segment of Lib Dem support for which the Tories have always been the enemy.
The end result is that Mr Clegg may well now face a leadership challenge, if not from fellow Cabinet member Chris Huhne, then quite possibly from someone outside the Coalition such as former deputy leadership candidate Tim Farron.
Given the Lib Dem collapse on his home territory of Sheffield, he may struggle even to remain an MP at the next election.
On the face of it, probably his best chance of retaining his seat would be to do something which many of us think he should have done a long time ago.
It is to join the Conservative Party.