In demanding a two or three week circuit break, Sir Keir Starmer’s announcement yesterday called time on Labour’s support for the government’s Covid strategy. That break-up was a long time coming. But how many sleepless nights preceeded the decision? Was it a reflex response to worsening transmission rates or something long premeditated?

Government sources were quick last night to circulate the line that Starmer’s breaking ranks was a piece of calculated chicanery from the flakiest of fair-weather friends. Sir Keir is, the government sought to place on record, “a shameless opportunist playing political games in the middle of a global pandemic”.

At last Wednesday’s PMQs, Starmer had asked Boris Johnson to provide the evidence for why 10pm curfews were necessary. In doing so Starmer – perhaps teasingly, perhaps because his mind is as nimble as a field mouse in a grain store – created an expectation amongst Tory rebels that Labour might join them in yesterday’s division lobby. Instead, Starmer has opted to attack the government from the opposite direction: not that pubs and restaurants should stay open after 10pm but that they, and most other non-essential activities, should – for a period – not open at all.

At PMQs today, the prime minister wanted to know what sort of leader of the Opposition could support government policy on Monday, but request his MPs to abstain on Tuesday’s votes that put such policies into effect, and by today be all for a short, near total, lockdown.

his mind is as nimble as a field mouse in a grain store

Starmer can protest that his view has evolved with the evidence, his case strengthened by the release of Sage recommendations from 20 and 21 September in which the scientific advisory group for emergencies struck a lukewarm note on 10pm curfews and the efficacy of the test and trace strategy whilst seeing much greater value in a circuit break. Labour sources are suggesting Sage’s recommendations back-up, rather than were directly responsible, for Starmer’s intuition. At any rate, they allow Starmer to suggest that it is Labour, not the government, that is “following the science”.

At PMQs today, the prime minister endeavoured to open an internal Labour wound, suggesting that in calling for the shutdown of public places, businesses and offices, Starmer was contradicting the leaders of Leeds, Liverpool, Manchester and Newcastle (all Labour councils) who insist that their cities are being destroyed by the tougher restrictions already imposed upon them. It did not quite work, because Starmer revealed that Greater Manchester was playing ball with him on the circuit break and that even the Tory leader of Bolton was a convert to circuit breaking (Bolton’s Tory leader, David Greenhalgh, duly responded that he was not pro-circuit breaking and was “disgusted” by Starmer enlisting him to his cause).

Whatever the mood in Bolton, instant polling suggests Starmer’s circuit breaker policy is overwhelmingly popular – especially with existing Labour voters and what remains of the Lib Dem core. However, transforming the political status quo requires winning over a significant share of those who voted Conservative in 2019, and here support for further social and economic sadomasochism is less ecstatic. Would a return to high death rates (as distinct from high transmission rates) shift this group to see things Keir’s way?

In the hard winter to come, the prime minister now faces opposition on two fronts. Labour decries the government’s strategy (that it supported until yesterday) as an “abject failure” – to quote the deputy leader, Angela Rayner. The Opposition is now exactly that, with a clear line that it stands for more extreme measures to cut the transmission rate in contrast to a dilatory government that is inadequate to the task.

Yet, Starmer knows, and backbench Tories fear, that the government is considering a circuit break, if the three tier system fails. If Johnson does end up implementing a circuit break it is Starmer who has positioned himself to take the credit and to claim that more lives would have been saved if only the prime minister shared his decisiveness. The Labour leader has learned from Nicola Sturgeon the art of divining what the government is planning and jumping in first to take the credit. It is a tactic that has made precious little difference to Scotland’s Covid statistics, but it’s done no end of good for the SNP’s popularity. If Johnson does implement a circuit break he will get all the blame and none of the credit.

For the other opposition sits behind the prime minister. Instinctively against shutting businesses and bossing people in their own homes and recreations, the Conservative party supports his restrictions with the deepest reluctance. Forty-two Tory MPs voted against the curfew measures last night, but many more backbenchers support the prime minister’s approach only in the absence of a clearer option in the uncharted territories of responding to a new virus where nobody – experts included –can speak with unimpeachable authority about what works and what does not.

is the prime minister strengthened by being boxed in?

To hold to a middling course, Johnson can push back against colleagues like Matt Hancock and Michael Gove who push for tougher, deeper, restrictions, by retorting that he has to keep on board the more liberty-minded backbenchers around Steve Baker (and the Treasury). To his chancellor and irate backbenchers, Johnson can pose as the bulwark against far worse impositions demanded by Sage, some of his Cabinet colleagues, and the Opposition parties.

So is the prime minister strengthened by being boxed in? In principle, it is now very difficult for civil rights-minded Tories to defeat the imposition of further restrictions given that they can’t win a division without Labour support. Is it time, therefore, for them to give up and accept they can carry neither the House nor, it seems, majority public opinion?

The answer to that question comes back to whether the Labour party is led by a far-seeing paragon of principle or someone who is an effective politician.

Yesterday, Starmer announced to the television cameras that the government was not doing enough, but then advised his MPs to abstain on the measures they were introducing, when logically a half-hog is still better than no hog. Would it be beyond Sir Keir’s strategic foresight to see opportunity in supporting future Tory rebellions against regulations they think go too far not because he believed that to be true, but because anything that opens chinks in the government’s armour ultimately serves the greater purpose of weakening Johnson’s claim to authority?