The Lib Dems have hung on to Eastleigh after a victory described as “stunning” by leader Nick Clegg.
The UK Independence Party (Ukip) – whose policies we have FactChecked in previous posts – was celebrating too after beating the Conservatives into third place while Labour came a distant fourth.
The surge in support for Ukip was described as a “protest vote” by the prime minister. But the party’s leader Nigel Farage disagreed, saying: “People will say it was a protest vote, but who we attracted here were non-voters who had not voted for 20 years – they are not protest votes.”
A Ukip spokesman told us the trend was so marked that “you can’t call this a protest vote as much as something completely fresh and different in British politics”.
If it’s true that the party is attracting voters who have been dormant for years, rather than just stealing support from other parties, that is indeed an intriguing new development.
Various opinion polls suggest that not all Ukip voters are disaffected Conservatives, a point made both by Mr Farage and by the Conservative Education Secretary Michael Gove, who said: “Broadly the same number defected from the Lib Dem camp as moved from the Tory camp to vote for Ukip.”
Mr Gove is right, depending on which research you look at. A poll by Survation found that A full 31 per cent of votes came from both ex-Tory and Lib Dem voters, as this Survation chart shows.
A Populus poll done on the eve of the election showed that 17 per cent of people who said they would vote Ukip backed the Tories in the last election in 2010.
Some 11 per cent said they had voted Lib Dem and 10 per cent had previously supported Labour.
The Survation poll is also cited by Ukip as evidence that they are attracting large numbers of non-voters. The results suggest that a significant number – 15 per cent – did not vote at all in the last election.
That doesn’t mean those people “had not voted for 20 years”. Survation didn’t go into that amount of detail when they carried out their surveys.
And the other major pollsters we have spoken to can’t prove Mr Farage right or wrong on this either. The polling companies generally ask people who they voted for last time, but don’t go back any further.
Dr Robert Ford, a politics lecturer from Manchester University who has been researching Ukip’s rise in popularity, told us there is evidence in more detailed questionnaires carried out by the British Election Study that Mr Farage may be right about the party attracting long-term non-voters.
Dr Ford said: “Ukip voters consistently come out as more negative about every aspect of the political system, the mainstream parties and the act of voting. People who don’t think they are being given a meaningful choice tend to stay at home more often.
“I think Nigel Farage has a point.
“These voters are not just disgruntled Tories or disgruntled Lib Dem voters. It is much broader than that. There is a broad-based sense of disaffection and it’s right across the political spectrum.
“Part of what Ukip is picking up on is a more deep-seated disaffection from politics as a whole. And don’t forget that non-voters are the largest slice of the electorate – more than 40 per cent.”
Dr Ford says that despite its historic emphasis on withdrawing from the EU, the party’s main focus is now immigration, an issue that enables it to steal votes from all the mainstream parties as well as the far right.
A surge in support for smaller parties among people who are disillusioned with the political establishment is a Europe-wide trend at the moment, he added.
Eastleigh could well be something far more complicated than just a mid-term protest vote against the coalition.
There’s good evidence that a significant number of Lib Dem voters and a good few people who backed Labour in 2010 voted for Nigel Farage’s party this time.
And there is some evidence that a fair number of people who voted for Ukip may not have voted for anyone at the last election.
That doesn’t quite prove Mr Farage right when he says people who hadn’t voted for a generation came out for Ukip last week – but it’s certainly a possibility.
All of this should be food for thought for the three biggest parties as they face the threat of a hidden demographic preparing to register its disillusionment with mainstream politics with a vote for Ukip.