RULE 17b of politics: never over-promise and under-deliver. 

The problem for Boris Johnson is that disregarding this basic tenet of wise government seems to be written into his political DNA; he just can’t help himself. 

Having suffered a backlash over the HS2 row and its missing Leeds link, the PM has now whipped up another one on social care in England; dubbed by Labour the new “working class dementia tax”. 

Yes, by putting a lifetime ceiling on costs for care the UK Government is making the situation somewhat better than the present one, where there is no ceiling.

And we are told no one will have to sell their home while they are alive if they need residential care. 

But the Conservative manifesto promise was that no one should have to sell their home to pay for care in any circumstances. 

At a rumbustious PMQs Boris was at his most boosterish when he asserted that a person’s house would not be included in the calculation of costs; it would disregarded. 

But this flies in the face of reality. If a person owns a house worth £150,000 and it is their only asset, how are they supposed to pay for care costing up to £86,000? So, what the PM said was simply not true. 

A person, say, with dementia needing full-time care might not have to sell their home while they are alive but most of its value could go to the taxman after their death, thus leaving their loved ones with a much smaller inheritance. 

Last week, a policy paper showed that only personal contributions would count towards the cap for people who received financial support from a local authority for some of their care.

This means poorer individuals will reach the cap faster than those who are wealthier and so will see more of their assets eaten up by care costs. 

Johnson, with a deal of justification, had a pop at Labour’s approach, noting how in its manifesto the cap on social care south of the border was put at £100,000. “They haven’t had the guts to fix this in all their time in office, it’s something left over from the Attlee government and we are fixing it,” declared Boris.

 After the PM’s rambling CBI speech – notable for his references to Peppa Pig, Moses, impersonating a car engine and missing his place for several seconds – Keir Starmer couldn’t resist a bit of sarcasm by enquiring after his well-being. “Is everything OK, Prime Minister?” he asked with a grin.

Ian Blackford for the SNP was not going to miss out and declared: “Officials have lost confidence in him, Tory MPs have lost confidence in him – the letters[of no-confidence] are going in – and the public have lost confidence in him. Why is he clinging on when quite simply he isn’t up to the job?” 

Westminster-watchers know when a leader is in trouble; when the troops are conspicuously overly supportive.

After last week’s PMQs when there were empty spaces on the Commons benches all around Boris, today’s ritual ding-dong got underway with loyal backbenchers roaring their approval. No one was fooled. 

How can anyone forget Iain Duncan Smith’s notorious “the quiet man is turning up the volume” conference speech of 2003 when he received 19 standing ovations and, to top it off, another eight- and-a-half minutes of cheering at the end. Yet within a month he resigned as the Conservative leader following a vote of no confidence by his party. 

Tory MPs are now routinely rebelling against the party whip - that is, the PM’s orders - as discontent continues to break out.

One No 10 source, dubbed the “chatty pig” for obvious reasons, declared that Boris’s premiership was “just not working”. 

They said: “Cabinet needs to wake up and demand serious changes otherwise it’ll keep getting worse. If they don’t insist, he just won’t do anything about it.” 

Indeed, one disgruntled Tory MP told the PA news agency Johnson was “losing the confidence” of his backbenchers and should quit in the New Year. 

“He is a lovable clown, the problem is no-one is laughing anymore, are they?” 

The backbencher would not say whether they had submitted a letter to the 1922 Committee of Tory MPs calling for the party leader to quit. But a whip was quoted as saying it was an “assumption” that some MPs had sent no-confidence letters to the 1922 Committee. Which is not a denial. 

If 15% of sitting Conservatives submit letters, then there would be a vote on the leadership, although the whip insisted: “It will not get anywhere near the 50 letters you would need,” adding: “But it does cause angst.”

The image of Sir Anthony Meyer, the pro-EU Old Etonian “stalking horse” baronet, who stood against the increasingly autocratic Margaret Thatcher in 1989 sprang to mind. He lost of course but the purpose of the challenge was to damage the leader, which it did.

She would, of course, face a more serious challenge from Michael Heseltine a year later, which ultimately led the wounded premier to stand down. 

Yesterday, the PM was urged by some of his Tory colleagues to bring into No 10 a political heavy-hitter to help turn things round.

One ex-minister noted: “He’s absolutely got to do something. All of us have weaknesses; it’s incumbent on us to put the right people in place to correct for those weaknesses.” 

Thatcher’s famous phrase of “every Prime Minister needs a Willie” – a reference to her loyal and experienced deputy Willie Whitelaw – has been heard after suggestions were made that Downing St is populated largely by young, inexperienced hands. 

Dominic Raab, the Deputy PM, did his best to bolster Boris by insisting there was a “steeliness to him” and that he was focused on the job. 

But the Justice Secretary, in reference to that speech, admitted there was an “ebullient, bouncy, optimistic, Tiggerish” nature to his demeanour. Likening your boss to what has become an animated cartoon character is not, one could argue, the wisest of moves.

Raab dismissed talk of no-confidence letters being sent to the grey-suited men of the 1922 Committee as “tittle-tattle”. 

Downing St, meantime, was forced to insist that the PM was physically “well” and “focused on delivering for the public”. 

The problem for party leaders who over-promise and under-deliver is that, come election time, the voters quite understandably will ask themselves can they believe what is being offered, if, previous pledges have been routinely dishonoured. 

From tax rises to the pension triple lock and now on social care in England, Boris has broken a trio of manifesto pledges.

Voters don’t forget and he may pay a heavy price at the upcoming North Shropshire by-election caused by yet another row over former Cabinet Minister Owen Paterson breaking parliamentary lobbying rules. 

More importantly, the PM may also pay a heavy price at the next General Election; that is, of course, if he makes it that far.