Notwithstanding the defection of UKIP MEP Martina Andreason last Saturday, the Tories look set to lose the Eastleigh by-election on Thursday thanks to a surge  by Nigel Farage's party.
Now routinely hitting 8-12 per cent in national polls, UKIP’s rise might not be enough to break our three-party system, but it may see them improve on their position in next year’s European elections and perhaps deprive the Tories of an overall majority in 2015 by splitting the centre-right vote as the Cameroon Tory party tacks to the centre; leaving UKIP space to pick up alienated social conservatives with a penchant for small-state solutions and a disavowal of all things European.
But why does this not work on the other side of the political aisle? Why is there no effective leftist challenge eating away at Labour’s core support? On the face of it, it seems anomalous. As Labour moved to the right under Tony Blair from 1994 onwards, enormous amounts of political space opened up on the left.
Arthur Scargill’s Socialist Labour Party , born of the decision to scrap the Clause IV commitment to large-scale nationalisation, was the first to try and fill it back in 1995. Both the Socialist Alliance  and George Galloway’s Respect party  have also unsuccessfully attempted to occupy Labour’s left flank. Granted, Galloway has now poked Labour in the eye on two memorable occasions; beating pro-Iraq war Blairite Oona King in Bethnal Green and Bow in 2005 and then, last March, winning the Bradford West by-election. But these were aberrations and no wider breakthrough has followed.
There’s a reason for that. Well, actually there are three. The first is organisational. Setting up a political party requires cash – rather a lot of it. Without hefty benefactors, this is an insurmountable problem for left-wing pretenders. The trade unions offer Labour both finance and organisation. Those who see the relationship as solely monetary miss the point. Labour’s affiliated unions supplement the party’s activist base with a reserve army of committed, well-organised and politically-motivated supporters. Without the trade unions, no left-wing alternative to Labour stands a chance.
The second reason is that idealists have simply taken to the streets. From the Stop The War movement through to UK Uncut, new grassroots movements, relying on social media, rather than union funding, are reinventing the left as oppositional mass protest. The compromises of constitutional politics, as Ed Miliband’s Marxist theorist father, Ralph, noted  in his book, Parliamentary Socialism, means that many left-wing idealists, who would in previous years have caused problems for Labour’s moderate leadership, are now happy to bypass party politics altogether.
The third reason Labour faces no effective challenge from the left is down to existing choice, at least for voters on the Celtic fringe. Although Labour would never admit it, both Plaid Cymru and the SNP are essentially social democratic parties, offering a viable, centre-left, anti-Tory alternative to wavering Labour voters. The choice for English voters though is essentially one of stick or twist; with twist in this instance being the option of not voting at all.
As UKIP threatens to reshape British politics by taking up permanent residence on the Tories’ right flank, David Cameron can perhaps be forgiven for wishing disgruntled Tories simply stayed at home too.