Suddenly the limits of a leader’s power come into full, glaring view: David Cameron has announced he will allow ministers to take a different public stance to him during the EU referendum campaign. He concedes this not because he wants to but because he has no choice, if he wants to keep his government more or less intact. As Cameron made his announcement Jeremy Corbyn struggled to complete his first reshuffle, seemingly taking almost as long as those leaders who negotiated the Treaty of Versailles after the first world war. He did not choose to take his time but could not act speedily. He is not in a strong enough position to be commanding.

Cameron has freed his ministers on the EU vote. Now his problems begin | Matthew d’Ancona Read more

Increasingly, and deceptively, UK politics is viewed as a presidential contest. Think of the focus on the party leaders during elections and between them. And the pivotal test of a leader’s success is his or her strength over their party. Margaret Thatcher was not for turning, even if her colleagues wanted her to do so. Tony Blair had no reverse gear as he lectured Labour vaguely about doing “the right thing”. Leaders must be strong. Leaders must be bold. In the UK they are expected to be as mighty as a president.

But they cannot be presidential, even if they try to appear so. They are leaders of parties, but are dependent on the support of their parties in order to lead. The current freakish situation makes the case vividly. Parties, or parliamentary parties, flex their muscles and the leaders have to respond.

In allowing ministers the freedom to speak against each other in public, Cameron is taking a risk. But not to do so would lead to resignations across his government, a formal schism before the campaign had even begun. He takes the only option available to him, as Harold Wilson did in 1975, the last time the UK held an in/out referendum.

These are only the latest steps in the dance – the deadly dance – between two sides

Wilson’s similarly enforced generosity kept his government together, but there is a very big warning for Cameron and his successor in what happened to Labour next. Once the spell of collective responsibility had been broken, it never properly returned. At one point during the 1975 referendum campaign the home secretary, Roy Jenkins, declared that he could not take seriously the economic views of the industry secretary, Tony Benn. In response Benn suggested that Jenkins was not being truthful in his claims about how little sovereignty the UK would lose. Such exchanges between ministers made it almost impossible for the facade of unity to be resurrected afterwards.

There will not necessarily be a repeat now, but Cameron has been forced to do what he pledged never to do. In its most extreme form he allows the Conservative party to bang on about Europe, with ministers battling it out in public. On other issues the Conservatives are far less divided than Labour was in the 1970s, but the experience of open debate over an issue that generates such passion will change the party for ever. Cameron has no choice. In tearing his party apart, he hopes to keep his party together.

Corbyn has not found a way to keep his party together in the first place and is not even wholly sure whether or not unity is his ultimate objective. He was elected on a distinct policy agenda that is opposed by most of his MPs. Does he cast aside his MPs in order to adopt his agenda, or bring them on board and drop some of his deeply held convictions? There are no obvious answers. Every twist and turn since he became leader arises from this bizarre context.

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As a party leader Corbyn is semi-powerful and semi-impotent. Periodically, such as after a byelection victory, he feels more powerful than impotent and is tempted to form a shadow cabinet closer to his viewpoint. When he tries to do so he discovers that he is partially impotent. Sometimes he exerts power and experiences impotence simultaneously, which is why his shadow cabinet reshuffle was the longest in history. Receiving conflicting advice from his inner circle about the virtues and dangers of a sweeping reshuffle, unused to managing big teams, facing resistance from shadow cabinet members threatened with change, and seeking more coherence on foreign policy, Corbyn was never entirely sure what scale of reshuffle he sought or could feasibly bring about until he set out on the arduous task.

Almost always, reshuffles highlight the limits of a leader’s power. But Corbyn, with no previous experience of working on a frontbench let alone appointing one, is uniquely tested. The constraints are heightened by the whirl of social media that makes leadership harder than ever. After the sacking on Tuesday from the shadow cabinet of Michael Dugher – a departure Dugher announced on Twitter – various of his frontbench colleagues tweeted their admiration and support for him, an unprecedented act of defiance of the Labour leader in the middle of a reshuffle. Shadow cabinet members feel free to differ with their leader even when the freedom is not formally granted.

There is no discipline partly because the situation allows for none. Some of Corbyn’s allies briefed, accurately, over Christmas that there would be a new shadow cabinet and that Hilary Benn should be moved from the Foreign Affairs brief. But such is the scale of Labour’s internal chaos that the briefings should not have been regarded as officially authorised. They were partly aimed at stiffening Corbyn’s backbone to act ruthlessly.

Labour’s war of attrition must end – or the Tories will keep running amok | Owen Jones Read more

But Corbyn is not a ruthless figure, nor has never had to be until now. In response to such imprecise briefings dissenters spoke provocatively of a “revenge reshuffle”, arguing disingenuously that the speculation was a distraction. They were the ones fuelling the media focus. These are only the latest steps in the dance – the deadly dance – between two sides.

As in all high-profile organisations, there has to be a pretence of unity in governing parties or parties that seek to govern. Without it, messages are incoherent and leaders seem weak. Leaders are always weaker than they seem, but the best of them wave a wand and convince us of their might. Now there are no conjurers, or parties are too restive for the tricks to work. For months senior figures of both parties will argue openly, spells broken and divisions aired. Their parties will be even harder to lead in the future.