As UKIP makes parliamentary gains at every turn, it no longer seems possible to dismiss the party as a group of anti-EU obsessives that has little in common with mainstream politics. The days of the swivel-eyed loon are over.

One of the most striking features of UKIP’s growth seems to be that it is based on increasingly diverse political support. Initially regarded as a refuge for disgruntled Tories, it has become apparent that the party’s support base can no longer be so simplistically characterised. Since the May 2013 local elections, Nigel Farage has taken every opportunity to argue that his party would henceforth be targeting votes from across the spectrum of major parties in the UK.

Research suggests that UKIP fares relatively well among older, less well-educated, white, working-class voters – especially men. These are the left-behinds who have not benefited from social and economic change in contemporary Britain. They are disillusioned with the major parties, embittered by immigration, and eurosceptic. But they are no longer necessarily disillusioned Conservative voters.

Once upon a time

Back in 2010, between 45% and 60% of UKIP supporters were ex-Tory voters and less than 10% were ex-Labour.

They were much more likely to read newspapers sympathetic to the Conservatives, such as The Daily Mail, The Express, and The Telegraph, and much less likely to read those favouring Labour, such as The Daily Mirror.

On a 10-point scale, where 0 rated as left-wing and 10 as right-wing, UKIP voters in 2010 located themselves at 8.23 on average. This was slightly to the left of where they perceived the Conservative Party to rate (8.74) but comfortably to the right of where they perceived Labour to reside (6.49).

UKIP’s working class supporters were distinct from Labour’s core working-class voters in several respects – they were more self-consciously right-wing, more exercised by issues of cultural identity, more immersed in the Tory press, less likely to live in Labour-held constituencies and, indeed, far less likely to have been Labour voters at all in previous elections.

The class of 2014

This classic UKIP profile has started to changed over the past 12 months. As support for the party has grown, it has encroached further and further into Labour territory. In Rob Ford and Matthew Goodwin’s top 15 parliamentary seats that are most winnable for UKIP, 12 are currently held by Labour.

And there are signs that UKIP has been making significant changes to its policies accordingly. Nigel Farage famously dismissed UKIP’s 2010 manifesto as “drivel” and announced a thorough review of party policy in 2013.Everything’s going exactly to plan.Stefan Rousseau/PA Wire

You now won’t see any references on the UKIP website about being “traditional conservative and libertarian”. Gone are promises about a flat-rate income tax. Instead, there is talk of introducing a graduated tax scheme that would be more palatable to Labour voters.

There is a clear defence of the NHS as something that should remain free at the point of delivery and the coalition government’s controversial bedroom tax will be rescinded. There will be no new Private Finance Initiatives – through which public infrastructure is funded by private money. Local authorities will be encouraged to buy out PFIs that are already running.

These policies all seem to be pitched at the left-behinds who are losing faith in Labour and it seems to be having an effect. Polling ahead of the Rochester and Strood by-election suggested that 40% of those who voted Labour in the constituency in 2010 intended to vote UKIP. That’s only only slightly less than the 44% of Tory supporters in 2010 planning to support UKIP’s Mark Reckless. That said, there are indications that most of UKIP’s key target seats are still held by Tories at present.

Forward planning

UKIP can’t expect to perform as spectacularly in a general election as in a by-election. The party will have to spread its still underdeveloped organisational resources over more than 600 constituency campaigns. Beyond Farage and his deputy Paul Nuttall, UKIP has few high-profile politicians that have been tried and tested in the harsh glare of national political campaigns and the intense scrutiny of a general election campaign is likely to highlight holes in party policy.

Even so, UKIP has been preparing for this election for a long time and has made sure that it will be the most difficult-to-predict contest in the post-war era. Another hung parliament is a distinct possibility. The outcome of such a scenario will depend entirely on the arithmetic and the strategic calculations of any party with governing or blackmail potential after the vote. And UKIP just might be a player in that game.

Paul Webb does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.