The nightmare scenario has come true.
Last night UKIP won its first seat in Britain's parliament in the Clacton by-election and is firmly established as the third biggest party in national polls.
It could find itself with more MPs after next year's general election, and, given how close Labour and Tory support is, it could conceivably find itself in government as part of a coalition.
The kind of policies a joint Tory-UKIP administration would enact don't bear thinking about; think how damaging the Conservatives have been to the state when partnered with Liberal Democrats, then imagine how a harder right-wing group would change things.
As we said yesterday, giving any power to UKIP would be a disaster for unemployed people in particular.
His party makes clear that it supports compulsory enrolment on workfare programmes, despite apparently standing for freedom and despite these programmes' poor records in supporting people into work.
They have provided no answer to the main complaint that workfare displaces paid work, reducing the number of real jobs available while providing taxpayer subsidies to private companies who get their workers paid for by benefits.
UKIP's low-tax standpoint means it favours lower public spending and will to cut benefits to support this, including reducing all welfare payments to the same 'basic cash payment' level.
Some of the more looney fringes of the party - and this is a party made up almost entirely of looney fringes - have called for unemployed people to be banned from voting.
Last year blogger Johnny Void revealed how UKIP had deleted a page on its benefits policies from its website, and that this had called claimants "a parasitic underclass of scroungers."
UKIP almost make the Tories look like Benthamites, and the only reason we don't know even more damaging information is because they refuse to provide it, or hide it when it is exposed as the frothing unthinking nonsense it is.
But what of the central platform of the party, leaving the EU?
Today sees the publication of an article by Jonathan Portes, the economist and head of the NIESR thinktank, on the subject.
UKIP has stated that free movement of workers from the EU into Britain harms the employment prospects of local people, but Portes skewers this argument comprehensively:
He says: "all the empirical evidence that we have suggests that any impact on unemployment from free movement of workers has been too small to detect statistically in the case of the UK."
New workers take jobs but also create opportunities, and create more demand through spending their wages, and this creates more jobs.
UKIP trades on many people's ignorance of the economic benefits of migration.
The Clacton win provides a foothold in British national politics that the party is likely to use to worsen conditions for the very people who voted for it.