It is only four months since Boris Johnson led the Conservative party to a historic victory. His 80-seat majority seemed to recast the electoral landscape for a generation. It also marked another milestone in Brexit’s transformation of the Conservative party from the party of business to the party of the flag. Today, that seems like another world.

Everything has been upended by Covid-19. The business of government is wholly taken up with protecting public health, keeping the economy on life support and, in Johnson’s own case, his personal survival. Today the national lockdown is expected to be extended into May.

It seems likely that the Britain which eventually emerges from the coronavirus crisis will be a country of a significantly different temper from the Britain that went into it. Nobody can be certain about the degree of change. The possibility that the economy may shrink by a third, with millions of job losses, is a reality check about a more enduringly difficult new normal. The post-pandemic Conservative party must adapt too. But in what ways?

Future British politics will not shake down into a binary choice between the economy and public health. The need to restore both will be far messier than that. Political horizons will simultaneously be very wide – global issues of health, supply chains, travel, information and Chinese power will surge up the agenda – and very narrow: local issues about safe ways to work, earn, live and survive a future pandemic will matter more too. Politics will be more fragile, fearful and dynamic.

While the pandemic and the lockdown hold sway, the official Conservative position is to ensure the least bad of all possibilities. The policy can be summed up by Rishi Sunak’s comments this week. “The single most important thing we can do for the health of our economy is to protect the health of our people,” said the chancellor on Tuesday. “It’s not a case of choosing between the economy and public health.”

However, once discussion moves on to the so-called exit strategy and to the post-Covid future, as it is now beginning to do, this begins to change. The choices do not suddenly become absolute. Instead they become competing calculations of the balance of risk in the interaction between the economy and public health, as and when the pandemic wanes. That has to be one of the reasons why Keir Starmer is pressing the government to publish its strategy. He knows this will reveal faultlines and compromises that an opposition can exploit without appearing partisan or unpatriotic.

There are some signs of those tensions already appearing within Conservative ranks. Sajid Javid, Sunak’s more fiscally cautious predecessor, warned this week against mortgaging the future, and said low taxes remained key to kickstarting the economic recovery. Theresa May and several of her ex-ministers, including Philip Hammond, believe something similar. But Johnson will want to go on spending, not reinventing austerity. So will the health secretary, Matt Hancock, who will press for a large programme of resilience measures in health and social care to guard against a future pandemic. The new Tory MPs from the former industrial areas will agree with them. So, at least for now, will Sunak.

Where this process of change will eventually lead the Tory party is difficult to predict. Sunak’s autumn budget – in which the social care agenda that was abandoned in 2017 will surely have to be a central focus – looms increasingly as a vital moment. But all this will surely generate a rather different party, and with rather different priorities, from the one that Johnson led to victory last December.

Whether the Tory party successfully embraces the choices that will now face it depends overwhelmingly on Johnson himself. After 2019, the party is unusually dependent on the man at the top. The reshuffled cabinet consists mainly of minister of state-level players whom Johnson dominates from No 10. Its lack of depth has been cruelly exposed in the crisis. The party remains very much Johnson’s own brand, held together by his inimitable personality and popularity.

For as long as Johnson remains out of action, the important choices about the party’s direction are likely to be deferred. The party which, only a few weeks ago, Johnson and Dominic Cummings were building on the basis of Brexit and the anger of the left-behind is becoming less relevant by the day in the shadow of coronavirus.

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The dissonance between the new realities and the recent past is now huge. Instead of the old contempt towards experts, competence and seriousness, there is now a craving for all three to help steer a safe course through the Covid-19 crisis. The idea that the government’s post-pandemic priorities might include lighting fires under the BBC, the civil service and the universities therefore seems even more destructive now than before. The idea that Britain should be a Brexit buccaneer, turning its back resolutely against Europe and throwing itself into the arms of Donald Trump seems even more irresponsible.

As one former minister put it to me this week: “The party that was being created in the wake of the election was a new one. It was based on a cultural backlash against liberalism and established elites at home and abroad. But that doesn’t feel to me like what the country wants now. It doesn’t want divisive politics. It doesn’t want a culture war. This feels like a moment to step away from a lot of that.” Whether to take that step away will be very much Johnson’s own decision. But it is a decision with momentous implications for the Tory party and for the whole of British party politics.

• Martin Kettle is a Guardian columnist