Amid the tumult of Jeremy Corbyn’s leadership of the Labour party, a theme increasingly debated among so called ‘moderates’ is whether Labour deserves to survive the next decade as a mainstream political party. Those who find Corbyn’s leadership style and political positioning on totemic issues such as Trident renewal and Syrian intervention beyond the pale talk openly of forming a breakaway, centre-left party akin to the Social Democratic Party (SDP) in 1981. For all the speculative chatter, however, such an event is extremely unlikely to happen; here’s why.

Firstly, for all their protests Labour moderates can scarcely complain about the leadership selection procedure that brought Corbyn to power. In 1981, the dominance of the left and the demise of Labour’s social democrats was underlined by the dramatic, set-piece special conference at Wembley – not on the question of unilateralism or Europe, but the make-up of the party's Electoral College. Rule changes meant the unions had 40 per cent of the votes in the selection of Labour’s leader with 30 per cent for the constituencies; MPs were reduced to 30 per cent, undermining the constitutional pre-eminence of the Parliamentary Labour Party (PLP). For beleaguered right-wingers, the soon to be founders of the SDP, this was an emblematic issue on which to fight. Factional conflict between revisionists and the party’s left has often taken place against the backdrop of disagreement over conference procedure and the party constitution. Yet Corbyn's leadership victory was the product of a slow moving organisational “car crash”, conducted under the one-member-one-vote rules the Labour right had championed since the Gang of Four.

The political scientist Robert McKenzie conducted a seminal analysis of the basic power structure within the Labour and Conservative parties of the 1950s. He found that, in both parties, authority ultimately rested ‘with the parliamentary party and its leadership. In this fundamental respect the distribution of power within the two major parties is the same'. While his plans are still fairly opaque, Corbyn intends to overturn the established power structures; increased policy-making powers will go to the NEC, and the possibility of contentious issues being debated by impromptu party plebiscites has been canvassed. Again, the irony is not lost on either the left or right that in 1995 this same system, or something like it, was used by Blair to gain legitimacy for changes to Clause IV.

Secondly, in the early 1980s the SDP’s pitch was towards a politics of centrist ‘moderation’ against the extremes of the Bennite Left and Thatcherism; today, UK politics is defined by new faultlines that transcend the traditional boundaries of left and right: between ‘the elite’ and the ‘outsiders’; and in Scotland and Wales between ‘nationalists’ and ‘unionists’. This makes the centre-ground far more volatile and unpredictable.

Importantly, it indicates that revisionists and social democrats in the party face an existential challenge. If in an age of 'anti-politics' party democracy and mass decision-making is synonymous with ‘radicalism’ rather than moderation (the opposite to what political scientists had long assumed), is there any real demand for a political brand defined by its essential moderation? For one historian, the SDP was an avowedly middle-class ‘insider’ movement, 'a delighted act of self-recognition by a new class coming out and discovering its common identity'. In contrast, today’s new political movements are defined by representing a long-ignored strata of society, having sprung up internally within the Labour party (Corbyn's supporters) and on the radical right (UKIP).

Thirdly, the descendants of the SDP, the Liberal Democrats, provide further evidence that centrist politics is passing into abeyance. Any new party would need immunity from the toxicity that the Liberal Democrats acquired having entered into a governing coalition with the Conservative party. In the early 1980s, at least within Roy Jenkins' inner circle, the fact that the Liberal vote and organisation could be harnessed – and that the SDP-Liberal Alliance would go some way to resolving David Marquand’s ‘progressive dilemma’ by healing the breach between the left and liberalism – was a significant part of its appeal. While David Steel’s Liberals had suffered a decline in support in the 1979 general election, the result had been significantly better than many predicted.

Today, in contrast, the relationship of Tim Farron’s party with social democracy is unclear, as is the question of how electorally useful they could be to any centrist political force. Constitutional and electoral reform might provide a lightning rod to unite disparate progressive forces. Yet there is presently little agreement on this question across the Labour and Liberal Democrat parties: Labour figures have remained notoriously circumspect about changes to the electoral system; even in 1981, after agreeing to a pact between the two parties, Shirley Williams inquired: ‘does that mean I’ll have to support proportional representation?’

Fourthly, an ‘SDP Mark II’ is unlikely precisely because it failed in the 1980s, while the Labour party ultimately recovered under Neil Kinnock’s leadership. One of New Labour’s architects, Philip Gould, was able to describe the project as a ‘new party created within the structures of the old, like a butterfly trapped within his own chrysalis’. The gradual rejuvenation of Labour’s electoral appeal between 1983 and 1997 indicates to the Labour right that evolutionary progress is possible once a party recovers the appetite for power. On the other hand, the SDP is often spoken of as a parable for the dangers of ‘splinter parties’.

Political parties have an 'institutional memory'; history matters while contemporary history matters even more. For members of the current parliamentary party, Blair’s rise, and the SDP's decline and fall, are potent memories. The transformation of British politics at the start of the twentieth century that resulted from the rise of the Labour party and the emasculation of the Liberals, provides a stark warning that parties cannot be insulated from electoral reality, even if it is a less immediate point of reference for those analysing the risks of inaction today.

Finally, there is currently no viable political leadership for a breakaway social democratic party. Groups like ‘Labour For the Common Good’ have been criticised for their ambiguity of purpose. Of course, the Gang of Four’s Council for Social Democracy – the progenitor to the SDP – had uncertain beginnings. At the press conference announcing the Council’s creation, a reporter asked what it was. ‘I think the statement makes it perfectly clear’, hoped David Owen. ‘Well, what’s a council?’, the journalist pressed. ‘It’s a very useful body’, Jenkins replied. Yet, fairly swiftly, the Gang of Four’s purpose became clear. The Council for Social Democracy, with its talk of a major ‘realignment’ of British politics, was a clarion call for action; and the Gang of Four were all experienced former Cabinet Ministers with political reach across the labour movement, including (in the case of Shirley Williams) the trade unions.

Hunt and Umunna’s grouping is different. Their meetings have debated the case for ‘tactical alliances’ and an end to progressive ‘sectarianism’, reminiscent of David Owen’s recent call in the New Statesman. But the right of the party are providing a call for calm rather than a call to arms. Despite the obvious historical parallels, while the mould of British politics is currently threatening to strangle revisionist social democrats, a period of stasis rather than dramatic sea change appears more likely.