For all the barrels of ink spilled and pixels pressed into service predicting the outcome of next year’s election, there are only two trends that matter. The first is the rise of Ukip, gouging support from the Tories’ right flank; the second is the evaporation of the Liberal Democrats, who won 23.6 per cent of the vote at the last general election but could poll in single digits at the next one.

Both trends should give Labour’s spin doctors pause, because when those refugee Lib Dems were looking for somewhere else to go, relatively few of them headed Milibandwards. (A 2011 analysis by Mark Pack found that, of the previous year’s Lib Dem voters, a quarter had stayed loyal, a quarter had shifted to Labour, a quarter had switched to “don’t know” and the rest were “scattered across the other options”.) Is the lack of a left-wing alternative to Labour something the party can count on in future parliaments, or just a fluke of this one? Will there ever be a “Ukip of the left”?

On the face of it, there is certainly space in British politics for a party beyond the edge of Labour. Roughly two-thirds of the public want the railways renationalised but Ed Miliband is only prepared to offer a state company the ability to bid alongside private firms. A similar proportion of people want the utilities taken back into public ownership. Meanwhile, in Scotland, the SNP has recently sold itself explicitly as a left-wing party, willing to fund goodies that would have George Osborne crying “spendthrift” at Ed Balls. When Leanne Wood became the leader of Plaid Cymru in 2012, she proudly described herself as a socialist, adding: “I think there’s a natural left-ness in Wales that is reflected in Plaid Cymru.”

“The radical left has remained constrained by its tendency to focus on esoteric economic arguments, to implode due to infighting and generally steer clear of highly salient issues that it is uncomfortable addressing, like concerns over migration and national identity,” says Matthew Goodwin, an academic who has studied the rise of Ukip. “But there is still ample potential support for a radical left alternative, particularly if it launched a populist critique of Labour’s timidity and the failure of established political and financial elites to address issues like inequality.”

At this point, some of you will be picking up your pens to remind me of the existence of the Green Party. Sheathe them, please. Generous predictions have it on 6-8 per cent of the vote and it is struggling to hold on to its only MP, Caroline Lucas, against a Labour charge in Brighton Pavilion. To survive, Lucas has had to distance herself from the Green-led council, which has been plagued by the kind of “loony left” headlines that damaged Labour in the 1980s. “A ban on bacon butties,” roared the Daily Mail in April: “Traffic-calming sheep . . . the all-too-real story of how Britain’s loopiest party took over Brighton”. (It reported that the Greens were split between moderate “mangos” – yellow on the inside, like Lib Dems – or leftist “watermelons”, who are secretly red.)

A few months earlier, the more sympathetic Guardian had reported on Lucas siding with striking binmen against her colleagues on the council and asked: “Have the Greens blown it in Brighton?” So much for hopes that the Greens might emulate Charles Kennedy’s strategy of rolling the pitch for parliamentary candidates by building support at council level.

Of course, Lucas is not the national leader of the Greens – she was succeeded in 2012 by Natalie Bennett, a former journalist. But few people, even in the Westminster bubble, are aware of that, which points to another problem that the Greens have, compared to Ukip and Nigel Farage. (You can get a long way in British politics with the ability to be funny on Have I Got News for You.) Bennett’s decision to stand again in Holborn and St Pancras, where she got 2.7 per cent of the vote last time, has provoked grass-roots grumbling: why divert resources from a winnable seat to an unwinnable one?

Outside the Greens, the prospects for a radical left are even bleaker. The old hard-left organisations have collapsed, with the Socialist Workers Party imploding after rape allegations against a senior member and with a potential successor, the International Socialist Network, folding over discussions of baroque sexual practices on Facebook. The People’s Assembly Against Austerity has held successful rallies across the country, including one in June headlined by Russell Brand and attended by 50,000 people, but it has no aspirations to become a formal party and sees itself as a broader counterweight to austerity narratives.

Perhaps the fate of the National Health Action Party gives us a clue where the problem is. The group focuses on the NHS, which makes voters reliably misty-eyed; it is run by doctors and nurses; and it has the affable comedian Rufus Hound to sell its message in the media – yet it came only ninth in the European elections in London. That’s the difference between a grumble and a howl of betrayal. Voters might think Labour isn’t doing enough to protect the Health Service from those dastardly Tories but their exasperation hasn’t reached a sufficient pitch for them to give up on the party entirely. Similarly, the country might be to the left of Labour on rail and utilities but people don’t feel strongly enough about those issues for it to affect voting intentions.

There is one final factor: money. In recent years, Ukip has benefited from wealthy donors such as Paul Sykes, who spent £1.5m on a poster campaign for the party in April. There is a dearth of left-wing multimillionaires desperate to pour money into a new party and so far Miliband has managed to keep the big unions onside. If either of those things changes, we might get an answer to the question: “What on earth would a left-wing Nigel Farage look like?”

Read responses to this article from the Green party and Left Unity.