Ukip is that rare phenomenon in British politics, a lucky political party. Its current small, but significant impact has nothing to do with policies or even the projection of its reassuringly chirpy leader, Nigel Farage. External factors alone give them space on the political stage. Without these factors, Ukip would be nowhere. With them, the party is a force to be reckoned with up to the next election.

Above all, Farage should send a note of thanks to the Liberal Democrats for choosing the impossible challenges of power rather than an easy life in opposition. Before the Coalition was formed, the Lib Dems tended to be the protest vote of choice. Now Ukip is the most obvious vehicle for the lazily fashionable, thoughtless “plague on all your houses” vote. Almost certainly, the Liberal Democrats from the comfort of distant opposition would have won a by-election or two by now.

Intensity

Now some space is available for Ukip at a point when yet again Europe is a salient issue, arguably more so than at any juncture since the UK joined the Common Market, as it then was, in 1973. Once he has thanked Nick Clegg, Farage should express his gratitude to Conservative MPs who share his obsession with Europe thereby ensuring that the issue is viewed with a peculiar intensity.

Add in the third factor of tumultuous economic change, and a perfect storm is brewing for Ukip. If he had any more spare time perhaps Farage should send another note of thanks to the various senior bankers who played their part in the crash of 2008, fuelling a sense of fear and insecurity that then fuels support for smaller parties. In the 1970s, the last era of persistent economic crisis, smaller parties flourished or threatened to do so.

This is the background that makes the apparent bungling stupidity of Rotherham Council, taking foster kids from Ukip supporting parents, such a dream story for Farage and his party.

The Rotherham saga is publicity about Ukip, but not about what it stands for as a party. There is no such publicity. Smaller parties are not scrutinised in Britain. Even the Liberal Democrats got off very lightly before they joined the Coalition. Conservative and Labour leaders and now Clegg have to move with extreme care, every word and announcement analysed endlessly. Farage pops up every now and again knowing that interviewers do not see him and his party as likely to win a single seat at the next election let alone to form a government.

Such narrow national prospects allow for slippery evasiveness and lazy policy-making. Currently, Ukip proposes tax cuts and spending increases that would destroy the credibility of the bigger parties, but few voters will have studied the policies in much detail, even in relation to Europe. Anthony Wells, of UK Polling Report, tells me that Ukip attracts a lot of voters, not because of Europe, but on the broader basis that the Conservative leadership is not right-wing enough.

This is why Conservative MPs have good cause to worry. Ukip is insubstantial, incoherent, incredible and the most significant electoral threat to the Conservatives for decades. It is highly unusual for a potential split to occur on the right in British elections. Normally, the anti-Conservative vote divides several ways. In the 1980s, Margaret Thatcher won landslides partly because Labour and the SDP split the anti-Tory vote.

Crazy

In the New Labour era, disillusioned Labour voters tended to switch to the Lib Dems. The Conservatives had the admittedly limited political space to the right of New Labour pretty much to themselves. At the next election, it seems likely that disillusioned Tories will for once have the alternative choice of a party now being proclaimed as “mainstream”. No wonder some Tory MPs want an electoral pact based on the pledge of a pre-election referendum on Europe.

Such an offer would be crazy for David Cameron to make and I would be amazed if he were to do so. A pact with Ukip would indicate chronic lack of electoral confidence and a coming together on Europe that is not reflected in the fundamentally different positions of both parties. Cameron wants to remain in the EU. Farage wants to leave. Anyway, the last thing any Prime Minister would want in the run-up to an election is a make-or-break referendum. Cameron already faces one on independence in Scotland. To have two in advance of an election of uncertain outcome would be more than careless.

In one respect, Cameron and his party are lucky. Over time, the near-empty vessel of Ukip will sink. Indeed, assuming there is at some point a referendum on Europe, it would sink soon after the outcome were declared, its main mission resolved one way or another.

In addition, I doubt it would easily survive a change of leader. Bigger parties are fragile enough. Smaller ones are ultimately doomed. But for now, the party is on the stage acquiring momentum and enjoying good fortune. For Cameron, there is no scope for an electoral pact. Different parties rarely manage to negotiate such deals. Even the formal SDP/Liberal Alliance struggled to do so in the 1980s. Cameron has no choice but to take on Ukip rather than woo it.