The bigger Britain’s problems get, the more Labour seems to shrink. As almost every economic, social and public sector indicator flashes red, Labour politicians explain that regretfully they will only be able to do a limited amount in government about the worst set of interlocking crises in our modern history.

The more disenchantment with politics grows, the more narrowly Labour defines the kind of politicians and party members it wants. It excludes or marginalises Corbynistas, leftwingers in general, respected local government radicals such as Jamie Driscoll, and even the mild centre-left organiser Neal Lawson. The few clearly left-leaning figures who remain – for now – in the shadow cabinet, such as Ed Miliband, are briefed against by anonymous Labour sources in the Tory press. Meanwhile, Keir Starmer has increasingly regular chats with Rupert Murdoch.

There is a logic to all this purging and repositioning, lowering of expectations and policy trimming. It is the logic that has underpinned successful election campaigns by both main parties since 1997. From New Labour’s pledge cards, with their concrete but modest promises, to the Tory strategist Lynton Crosby’s advice to David Cameron to “get the barnacles off the boat” before his 2015 victory, electioneering in Britain has often been about discipline, repetition and minimising dissent and unnecessary commitments. It may not be inspiring or innovative, but it works, the advocates of this method argue. Look at Labour’s lead in the polls.

Yet poll leads and election victories take a party only so far. Once in office, especially at a time of national crisis – as Starmer is likely to be – the gap between wary campaign politics and the more risk-taking and imaginative mode that crises often require can create great tensions in a government. Sometimes premierships are destroyed by them. If Labour wins power, will Starmer’s supposedly safe strategy become a huge risk?

Despite the Tories’ claim to be the nation’s natural custodians, Labour usually takes office when Britain is in a mess. Unfortunately, such situations are the only time when many voters are prepared to give the party a try. One example of a cautious Labour government being overwhelmed in such a scenario is still infamous in the history of the party, even though it occurred almost a century ago.

In 1929, Labour won power with unemployment rising and industrial relations tense, just as they are now. Within months, the Wall Street Crash and Great Depression made economic and social conditions much worse. Yet the chancellor, Philip Snowden, like today’s shadow chancellor, Rachel Reeves, believed that Labour governments needed to prove their credibility by strictly controlling how much money they borrowed. He resisted calls to increase public spending, then supported cuts. The government disintegrated into pro- and anti-austerity factions. An early general election followed, in 1931, and Labour lost spectacularly, shrinking to 52 MPs. The Conservatives got 470.

Given the deep problems of the current Tory party, it’s hard to see it making such a dramatic recovery. But a Starmer government struggling with all the problems left by its Tory predecessors, as well as with inevitable fresh crises, while being blamed for everything by the rightwing press, and also attacked by some of the leftwing Britons he has alienated, is only too easy to envisage.

Yet a Starmer premiership doesn’t have to play out that way. Governments can rule cautiously, even in a period of crisis, if they are trusted. For the first two years of Tony Blair’s administration, Labour kept to the Conservatives’ existing spending plans, despite the rundown state of public services, and voters did not desert Labour in a disillusioned fury – probably because they believed, correctly, that better funding from the government would eventually be forthcoming.

A prime minister can also persuade enough of the electorate to be patient if they have a clear project. Margaret Thatcher’s long, divisive premiership was partly sustained by the belief of a decisive minority of voters in her vision of a more competitive society. Occasionally, Starmer tries to give a Labour government a similar grand purpose. In January, he promised “a fairer, greener, more dynamic country with an economy that works for everyone, not just those at the top”, and “a politics which trusts communities with the power to control their destiny”. So used are we to seeing him as Mr Cautious, these expansive moments do not get the consideration they deserve.

He lacks Thatcher’s and Blair’s communication skills, which enabled them to embed their main message even in everyday announcements. He also lacks their consistent quality: the sense that they had an ideology, whether you liked it or not. In three years as leader, he has already shifted from the continuity Corbynism of his initial pledges to the jittery patriotic centrism of his pandemic period to the more confident critic of Conservative Britain that is his current incarnation. In office, he could easily change again.

Optimists on the British left – there are still some – hope that he will be more radical in government than opposition, because circumstances give him no option. If public services are in even deeper crisis than now, after possibly another 18 months of Tory rule, then he will need new sources of revenue. With Labour’s ambition for Britain to have “the highest sustained growth in the G7” unlikely to be achieved quickly, if ever, and more borrowing ruled out, then this revenue will need to come from higher taxes. And with most taxpayers struggling financially, raiding the bloated stashes of the economic winners of recent decades is going to be very tempting – whatever reassuring things Starmer and Reeves say to the rich now.

Such a sequence of events could be wishful thinking. But it’s too early to say for sure how Starmer might govern. Next week, Labour’s national policy forum meets to help decide what goes into its manifesto. Further policy announcements are likely at this autumn’s party conference, and during the election run-up, which could include another Labour conference in 2024, if Rishi Sunak delays the election as long as possible.

If Starmer treats this whole period as an exercise in risk avoidance, and does the same in Downing Street, then he may join the list of failed British premiers. Helpfully, he has supplied future historians with a phrase of his own for governments that lack boldness: “sticking-plaster politics”. Let’s hope he has some stronger remedies hidden somewhere in his medicine cabinet.