Another day, another crisis for Gordon Brown. The Tories' win in Crewe and Nantwich is the party's first by-election win from Labour since 1978.
The 17.6 per cent swing would give David Cameron a majority of more than 100 seats at Westminster.
A BBC producer asked me to calculate how many seats Labour would lose in Wales on that swing. If you're a Labour MP you may want to look away now.
Rough back-of-envelope calculations suggest the loss of 13 of the 29 Labour seats - from the more predictable Vale of Glamorgan and Cardiff North to the rather less likely Cardiff South and Penarth and Cardiff West via Delyn and Newport West.
Talk of 13 losses may be fantasy politics. No-one expects a by-election size swing at the general election, but all but one of those six seats have been held by the Tories since 1979. There will be some anxious Labour backbenchers today.
They may draw comfort from the clumsy nature of Labour's campaign in Crewe, not just the "toffs" stuff but also the over-emphasis on their candidate as the daughter of Gwyneth Dunwoody. Tamsin Dunwoody may be a Dunwoody but she lives in Pembrokeshire, had few links to Crewe and playing the continuity card doesn't work when "time for a change" is in the air.
What would a Conservative government be like? London mayor Boris Johnson, the nearest we have to one at the moment, has been honouring his election pledge to publish the details and salaries of his senior advisors.
His chief spin doctor, my former BBC colleague Guto Harri, will be paid £124,364, twice the salary of a backbench MP.
That said, Guto will be appearing at the Hay Festival this week for the usual fee on offer - a white rose.