Scott Morrison’s reputation as a miracle worker took a big hit this week, as the national parliament resumed for its last few sitting days of the year.

To be fair, it wasn’t that the PM was unable to pull off unimaginable political feats, but that he failed on a much more mundane level – he and his senior ministers made a number of misjudgments that left the government shell-shocked and the man himself exposed to allegations of tampering with a police investigation.

You won’t be terribly surprised to read that a broken deal with One Nation leader, Pauline Hanson, was at the centre of one of the government’s damaging missteps this week. But we’ll get to that in a moment.

Far more serious than the obvious conclusion that one should never rely on a deal done with Senator Hanson was the Prime Minister’s apparent conclusion that it was perfectly okay for him to ring the head of the New South Wales police force – who he happened to know personally – to inquire about an active investigation into one of his senior ministers.

Considered through a non-partisan lens, it’s understandable that Mr Morrison did not want to set a precedent by standing down a minister who’d been referred to the police for political reasons. It could easily lead to a swathe of ministers cooling their heels on the backbench while maliciously instigated police investigations were completed.

But even if the PM simply wanted to confirm that the investigation into Angus Taylor, the Minister for Energy and Emissions Reduction, had been instigated due to the emergence of evidence that a law had been broken rather than an accusation by Labor, he should have done so on an arms’-length basis. Particularly given he knew the Police Commissioner. He has ‘people’ to do that sort of thing.

The PM is meant to govern in the national interest, not his own. And right now, people are asking themselves:

If one of my mates was under investigation, could I pick up the phone to the head of police and ask for details about that investigation on the day that it was launched?

— Anthony Albanese (@AlboMP) November 27, 2019

Instead, Mr Morrison’s supposedly legendary political nous deserted him, and he picked up the phone to chat to a mate about a topic that he shouldn’t have touched with a barge pole.

The reason for the PM’s misjudgment can be found in a time-honoured saying: pride comes before a fall.

Mr Morrison is so confident of his political superiority over the Labor opposition that he did not stop to think through the implications of phoning a friend to check whether Minister Taylor was in any real trouble with the police.

Now it is Mr Morrison who could face an allegation of having broken the law.

Hubris also sits at the core of the government’s serious misjudgment of Senator Hanson this week, resulting in a lost vote on one of its iconic pieces of legislation, the ‘Ensuring Integrity’ bill.

This was to give the government stronger powers to deal with badly-behaving unions and union officials.

We defeated the Ensuring Integrity Bill. Thank you to every person who stood up and said no to union bashing #auspol

— Sally McManus (@sallymcmanus) November 28, 2019

After weeks of Senate wrangling, the government’s senior negotiators believed they had come to an agreement with crossbenchers Jacqui Lambie and Senator Hanson on the IR bill.

But when it came to the final vote on Thursday, Lambie and Hanson and her One Nation colleague, Malcolm “Tin-Foil” Roberts, shocked the over-confident government by voting against the legislation and causing its defeat.

Senator Jacqui Lambie and Senator Pauline Hanson before the vote on the Ensuring Integrity Bill in the Senate on Thursday. Photo: AAP

Despite the government having agreed to incorporate some of Senator Hanson’s amendments to the IR bill in return for her support, the One Nation leader claimed this latest backflip was in response to the government’s weak reaction to the allegations against Westpac of breaching money-laundering laws.

Senator Lambie said she had also requested amendments to the legislation but had been rebuffed by government negotiators because they assumed they had locked-in the two votes needed from One Nation.

• Related story: Dutton’s dire warning to Hanson post-vote

It bears repeating – pride cometh before the fall.

Another bill pumped up by the government as an iconic issue is expected to come up for a final vote next week, which also happens to be the last sitting week for 2019.

This is the repeal of the so-called Medevac legislation that makes it possible for offshore asylum seekers with serious medical issues to be brought to Australia for treatment.

Senator Lambie announced this week that she had reached an agreement with the government and would support the bill on two conditions – one of which is secret, apparently on national security grounds.

I’ve had 10 journo’s put to me unsourced rumours about what I’ve proposed to the Govt – but I can’t comment on any. Only 3 offices know the condition – mine, the PM’s & the Minister. Everyone else is just speculating. #auspol

— Jacqui Lambie (@JacquiLambie) November 27, 2019

Whether this deal survives into next week may well depend on the extent to which Senator Lambie has been irked by this week’s events.

It will also depend on the PM being able to tap into any hidden reserves of humility (and common sense) that he may have on hand.