If the whole of opinion polling and almost all of paid political comment have any worth whatever, then the Conservatives will win the forthcoming by-election there.
But if they do not, then that will prove that in 2015 they won every seat that they ever possibly could.
That is enough for the barest of overall majorities.
But the loss of the tiniest handful would result in a hung Parliament.
The Liberal Democrats were already on course to win Remain seats in the South that were held by the Conservatives.
Indeed, they had already done so once, in a constituency where the Conservative majority had previously been of eye-watering enormity.
And then came yesterday's speech by the Prime Minister.
A hung Parliament in 2020 is now a racing certainty.
If Labour retained Copeland, then the Conservatives would be well advised to remove Mrs May.
Whoever was her successor would never have undertaken to invoke Article 50 by any specific date.
Or, indeed, at all.
Anyone who wanted that would need to vote Labour.