THERE is no more corrosive message in politics than “they are all the same”. To a significant section of the population who do not pay much attention, it is a lazy conclusion which rationalises reluctance to be distracted from matters they deem more pressing.

If they are “all the same”, then why bother to vote or have any respect for democracy? Why not just admire the fraud, the liar, the demagogue who promises to “get things done” without regard for consequences? If “they are all the same”, then why trouble to distinguish between right and wrong, decency and corruption?

For Boris Johnson, this is the get out of jail card. It is the gutter into which he will cheerfully drag British public life if it helps save his own skin. If enough of the electorate is prepared to exonerate him in the mistaken belief that he is no, or only a little, more rotten than “the rest of them”, then he may yet bound free.

It is a hugely depressing commentary on the state of politics that this is even a possibility and responsibility for whether it prevails rests exclusively, for the time being, with Tory MPs. It is for them to judge if the retention of Johnson is a price worth paying in exchange for the reputation of politics, their party and themselves.

READ MORE: Val McDermid's Goodwillie anger: How could football get it so wrong?

This dilemma was spelt out yesterday by Andrew Mitchell, a former Tory Chief Whip and, in my experience, a decent guy of old Tory stock. After telling Johnson to his face in the Commons that he “no longer enjoys my support” he went on the Today programme to say the current breakdown in public trust “is more corrosive than the expenses scandal and it will break the coalition that is the Conservative Party.”

That word “corrosive” again. In whose interest is it that a large part of the electorate simply writes off politicians as a class beyond redemption? The answer is that it is in the interests of populists who appeal to the worst instincts of the alienated and ill-informed. In other words, those who create the crisis of trust become its beneficiaries.

There is a Scottish version of this “othering”. The pretence that all politicians who oppose separation are part of the same ideological block is intended to wipe out a century of history and struggle. The economic and social dividing lines of politics are erased in order to establish a different dichotomy, around the constitution, as the only one that matters. Then empty rhetoric can prevail.

We see the process taken to its extremes by the Trump phenomenon in America. Trump’s abuse of every decent person and institution that got in his way fostered the mentality that made him President once and may do so again. If the swamp needs clearing, what does character matter in the bearer of that message?

That created an environment in which a physical assault on democratic institutions is endorsed by a substantial minority while faith in democracy plummets. A Washington Post poll found Americans’ “pride” in their democracy dropped from 90 per cent in 2002 to 54 per cent now. Johnson, the man with the Brexit bus, is leading us in the same direction but cares nothing for wider implications.

The stakes are high then for Tory MPs. I am well aware that they – never mind politicians in general – are not “all the same”. Most are honourable, decent, hard-working. We can disagree about many things but that is the legitimate battle-ground of politics. And time teaches that not everything any government does is wrong, far less malevolent.

From a party perspective, there would be no guarantee of benefit from Johnson’s departure. History shows that new leaders tend to be regarded as new governments, the Thatcher to Major transition being the outstanding example. The opposition interest may be best served by Johnson shambling into the next election, dodging scandal after scandal and hoping something will turn up.

That however is not a calculation which should be engaged in. Johnson should go because he is uniquely unsuited to the position he holds; because he has made a career out of mendacity; because he thinks nothing of telling the House of Commons a blatant lie; because, in the bizarre culture of Downing Street parties, he presides over exactly the traits of entitlement and contempt for decency that has characterised his life.

If someone better for the Tory interest emerges, then so be it but that should not be the first consideration, even for Tory MPs. Corroding the Conservative Party is their business. Corroding public life and respect for democratic institutions is far more serious and much more difficult to recover from.

Our columns are a platform for writers to express their opinions. They do not necessarily represent the views of The Herald.