Britain and the Quickfire Prime Ministerial Carousel

For much of the post-war period, Britain was famous for prime ministers who stayed in office for long stretches. Once they entered Downing Street, they were expected to remain. The dominance of two major parties, relatively disciplined parliamentary blocs, and the first-past-the-post electoral system typically turned ballots into workable majorities in the House of Commons, giving premiers a stable foundation. Margaret Thatcher and Tony Blair both enjoyed what seems almost unimaginable today: a decade in power.

But British prime ministers now come and go at a breathtaking pace. The country is on track for its seventh premier in a decade. Theresa May and Boris Johnson each served just over three years. Liz Truss lasted only 49 days. Keir Starmer was expected to be different when he entered Downing Street after Labour's landslide victory in 2024. Yet he too departed after barely two years. Why has Britain's once-vaunted stability so quickly given way to political chaos?

There are several obvious explanations, but none is sufficient on its own. Has social media fuelled political division? Almost certainly. But Britain is not the only country with the internet. Did Brexit make the country harder to govern? Yes. It cut across party lines, deepened political identities, and forced prime ministers to manage not just policy disputes but conflicting visions of what the country should be. However, as scholars note, Brexit did not spontaneously generate Britain's instability. It accelerated pressures already building within the political system.

Could it simply be that Britain suffered a run of poor leaders? For some recent premiers, the problem was competence. Theresa May could not get her Brexit deal through Parliament, while Liz Truss's radical economic experiment collapsed almost as soon as it began. For others, it was judgment and ethics. Boris Johnson broke the rules while demanding the country obey them, then compounded the damage by denying what happened. Keir Starmer blurred the lines: his government was marked by indecisiveness in policy but also by serious errors of judgment, most notably the appointment of Peter Mandelson.

But bad leadership does not explain everything. Britain has had poor and failed politicians before. The deeper problem lies in the changing relationship between the prime minister and their own party's MPs. Any premier needs their party's MPs to vote through their programme and defend them when they get into trouble. For most of the post-war period, that relationship was more reliable. However, since the 1970s, MPs have become readier to rebel against their party, challenge leaders, and, when necessary, help remove them. Borrowing the famous image of political scientist George Jones, a prime minister's power is like a rubber band. It can stretch, but only so far.

The fraying bond between MPs and the premier lies behind many major events in British politics since the 1990s. The Iraq War severely damaged Blair's authority with large parts of his party. In 2003, so many Labour MPs rebelled against Blair's Iraq policy that Blair and his aides feared it could cost him the premiership. The rebellion failed, but the war and its aftermath created a lasting rift between Blair and many of his MPs. David Cameron called the Brexit referendum because rebellious MPs in his own party, long hostile to Europe, kept pushing the issue. When voters chose to leave, he resigned. Boris Johnson's Partygate lies became deadly when his own MPs refused to back him. Keir Starmer's welfare cuts and harsh immigration policies forced Labour MPs to choose between loyalty and principle.

This rift makes MPs readier to act against the leader. Removing a prime minister between general elections is now a modern British habit. The last prime minister who both entered Downing Street after winning a general election and left after losing one was Edward Heath in 1974. Since then, leaders have more often been brought down by internal party pressure, scandal, resignation or succession than by voters directly ending their term at the ballot box. The habit is accelerating. Of the five most recent prime ministers, four left after pressure from within their own party, while only Rishi Sunak was removed by voters in a general election.

One final factor fuels the chaos: voters are changing. Britain is no longer a strong two-party system. In England, voters now split among multiple parties, rather than reliably backing Labour and the Conservatives as before. In Scotland, divisions over independence still shape politics. In Northern Ireland, elections follow a different party system, shaped by unionism, nationalism and a growing centrist tendency. In Wales, Labour now faces stronger challenges from Plaid Cymru and Reform.

This new electoral landscape makes life harder for both prime ministers and MPs. For leaders, victory is no longer simply about holding onto Labour or Conservative voters. It means deciding which voters to pursue, which promises to soften, and which part of the party coalition to risk losing. Keir Starmer's inner circle apparently believed that tougher immigration policies could hold or win back voters shifting towards Reform. But those policies alienated Labour MPs and created more space on Labour's left, where the Greens have shown they can win votes and seats from Labour.

Fragmented voting patterns also make incumbent MPs more vulnerable. When voters are less loyal and old party loyalties weaken, MPs have more reason to panic when their leader becomes unpopular, reckless or scandal-tainted. Rather than waiting for voters to judge at the next general election, they have an incentive to act earlier. That makes leaders easier to remove and prime ministers replaced faster.

Together, weak leaders, restless MPs and fragmented voting patterns have created a self-reinforcing vicious circle. Each failed premiership makes the next one harder. A new prime minister arrives promising restoration, but inherits the same deep problems, the same anxious MPs and even less patience from the public. Instead of restoring stability, each leadership change makes the next premier more vulnerable to being toppled.

That is the vicious circle Andy Burnham will inherit, and the question is whether he can break it. Burnham, who was Mayor of Greater Manchester from 2017 until returning to Parliament, arrives with a reputation among supporters as a doer and a plain-spoken political explainer. The by-election in Makerfield, where he won a seat to return to Parliament, gave them some evidence for that claim: Labour increased its vote there, bucking the broader trend of political fragmentation.

But much remains unknown. Not everyone believes Burnham achieved as much as his supporters claim in Greater Manchester. Public control over transport gave him a powerful story to tell, but national government will test those promises much harder. If he keeps Labour's harsh immigration policies, if promises of restoring public control prove thinner than voters expect, or if his popularity begins to wane, goodwill within the party could evaporate quickly. Then Burnham would face the same danger as his recent predecessors: MPs deciding that their leader has become a risk they cannot afford. That would put him right back in the vicious circle he was supposed to break.