It is a good idea, in politics, always to expect the unexpected.
But one of them, like it or not, has to happen.
I have been telling anyone who will listen these last few days that we should stop obsessing about the SDP: it’s lazy thinking and the political conditions are hugely different. For a start, the country had a competent leader, love or hate her, in Thatcher. And Labour had problems with Militant, but the lunatics had not, as now, taken over the asylum.
Indeed, it is more instructive to look at the Liberals’ split under Lloyd George and Asquith, or Labour’s under MacDonald, when the pieces were really in flux. Political blogger Professor Steve Fielding seems to have come to the same conclusion, at least on the first comparison.
It was clear that, given the dearth of love for Labour’s leadership within the vast majority of the parliamentary party, something would have to give at some point.
So, while it is not exactly unexpected, after three years of Corbynism and apparently no end in sight, that some decent and sensible-minded MPs decided to quit, perhaps the level of success they have enjoyed over the last few days since their creation, is.
We now have 20 independent MPs in the House of Commons, I would not be surprised if this were not the highest figure in postwar politics.
And it is almost as if the dam has now burst, and people have shaken off their fear. Those who have been cowed are starting not to be. They can see the smiles on the faces of those who can now look at themselves in the mirror for the first time in three years, and are thinking that perhaps risking their livelihoods might be a price worth paying for that feeling.
Whatever happens, this is clearly the biggest shake-up of two-party politics in the thirty-six years since the creation of the SDP (UKIP, we might remind ourselves, never came close to that level of defections).
There are now nine Labour MPs who resigned this week, eight within and one without The Independent Group, along with other previous resignees such as Frank Field, John Woodcock and Ivan Lewis. The group has also been joined by three Tories of some stature. In total, there are now twenty independent MPs in the Commons, the most to have been in that category voluntarily since the war, I’m told.
The real question, of course, is what happens next.
Momentum – if you’ll forgive the pun – is key: there now needs to be a steady-or-increasing flow of defections, to avoid the perception of a fizzling-out. But that flow looks more possible (apparently more defections on both sides may be announced this weekend). Watch this space. And yes, politics is suddenly exciting again.
Even if it does fizzle out, it seems likely that the resultant shock would be enough to knock Labour back on course eventually. And if it doesn’t, most probably because Labour finds itself unable to change, well, Labour will go the same way as the Liberals in the 20s – to oblivion.
Which, frankly, it will deserve to.