Ideology is not currently fashionable in the Conservative Party. Boris Johnson was, after all, elected primarily on the deeply pragmatic promise to “Get Brexit Done”, and his appeal was distinctively and deliberately non-partisan. This thing has happened, he said to the electorate, so let’s make the best of it and stop the endless (Theresa May-era) wrangling. December 2019 showed what a potent pledge that was.

We have had post-ideological prime ministers before. Tony Blair made a virtue of eschewing dogma and promising results, and the voters rewarded him handsomely for it. New Labour was, he cried, the political arm of the British people. So, in a way, the current Prime Minister has not defined himself by normal political metrics of left or right, big state or small government. He was faced with the enormity of the Covid-19 pandemic only a few months after his great general election victory, and so he concentrated on doing “what worked”, from furloughing and Treasury largesse to lockdowns and restrictions on civil liberties.

Earlier this week, some of his MPs kicked back. Although Johnson secured the support of the House of Commons for new restrictive measures to tackle the omicron variant of Covid, there were substantial rebellions against the Government. 100 Conservative MPs voted against the introduction of vaccine “passports” (actually a requirement to show vaccination status or a negative lateral flow test), while some also opposed measures to encourage working from home and mandating the wearing of face coverings in some public spaces.

One cannot make windows into men’s souls, but there was a common thread running through many of the rebels’ arguments that these measures were too restrictive, not supported by the known threat of the omicron variant, disproportionate and, more fundamentally, inimical to the way of life with which we are familiar. Marcus Fysh, the Yeovil MP, argued that we are not “a ‘papers, please’ society”, and, while his comparison with Nazi Germany was clumsy, his basic point resonated with many.

Only history will decide if it was coincidental that into this maelstrom fluttered a carefully posed and imposing Christmas card image from Liz Truss. The Foreign Secretary is pictured seated, flanked by an antique globe and a Union flag, the grand surroundings of King Charles Street tastefully glimpsed in the background. Its effect on the commentariat was electrifying: this, everyone was sure, was a portrait of a prime minister in waiting.

Liz Truss has come a long way in a short time. From the awkward backwater of environment, food and rural affairs and a blink-and-you-’ll-miss-it stint as Britain’s first female lord chancellor, she was a high-profile international trade secretary, generating energy and positive headlines when the cabinet at large was anonymous and moribund, and she has been richly rewarded with one of the great offices of state.

Along the way she has trimmed gently this way and that to craft her appeal. She is a believer in the free market, and in government having a more limited role in people’s lives. Lower taxes are part of her brand, and when she was number two at the Treasury she gave major speeches emphasising personal liberty and deregulation. She has even called her daughter Liberty.

It does not take much, then, to imagine that the Covid rebels, disgruntled by the overweening power of the state and chafing at strictures on personal freedom, might provide a cadre for a Truss leadership bid, should the top job become vacant. One could sketch out not a manifesto but some broad strokes: low taxes, free market, small government. There are 361 Conservative MPs; the support of 100 of them would be quite a coup for an ambitious minister.

Of course, as ministers and others repeat like nodding dogs, there is no vacancy. Boris Johnson is embattled, but he is a politician of preternatural resilience, and he may bounce back. But he is 11 years older than his foreign secretary, and, as Francis Urquhart wolfishly told the audience at the beginning of House of Cards, “Nothing lasts forever. Even the longest and most glittering reign must come to an end some day.”

There is no vacancy. Yet. But eventually there must be. One might reasonably say that Elizabeth Mary Truss can already perceive where some of the battle lines may be drawn, and where the forces will be concentrated. Perhaps she has drawn those lines herself.