SO Andrew Mitchell, having suffered the slings and arrows of self-inflicted misfortune for the best part of a very long month, is, as Ed Miliband so cruelly observed this week, "toast".

Truth be told, many at Westminster thought that after the toe-curling embarrassment of Wednesday's Prime Minister's Questions –when the stony-faced Chief Whip had to grin and bear the Labour leader's sustained verbal assault – he would survive, given David Cameron's steadfast loyalty to his bruised and battered colleague.

Indeed, after the midweek meeting of the Conservative 1922 Backbench Committee, at which more Tory MPs spoke out in favour of Mr Mitchell than against him, one senior party source insisted to the press the crisis was over. Nothing to see here; move along.

The party mood, the source insisted, was that the Chief Whip had survived the storm, the dog had barked and the political caravan had moved on.

Yet it seems clear that, after absenting himself from the Tory Party conference to avoid creating a week of bad headlines, on his return to Westminster the reality began to dawn on Mr Mitchell that his job was simply untenable.

Perhaps if he had been a departmental secretary of state then the Cabinet Minister might have been able to tough it out. However, as Chief Whip, the man responsible for looking colleagues in the eye and instilling discipline, Mr Mitchell has to command complete respect; as the week wore on, he realised he had lost it.

Perhaps the killer fact was that the month-long onslaught had some colleagues actually feeling sorry for him.

This, of course, is the last thing a Chief Whip needs; sympathy coupled with a lack of respect meant there was only one outcome. Plus, there was even talk that John Randall, the Deputy Chief Whip, had threatened to resign if his boss didn't.

Yet here we again have a Prime Minister who has given a colleague a second chance and stayed loyal to him. It worked with Jeremy Hunt and the jury is still out – metaphorically and literally – in the case of Andy Coulson, yet Mr Cameron's generosity of spirit did not work with Mr Mitchell.

After weeks of bad headlines the political emphasis of "plebgate" turned away from the Chief Whip and on to the Prime Minister and, most crucially, his leadership.

Sticking by his Cabinet chum for so long and so staunchly means Mr Mitchell's departure has caused even more damage to the PM's standing in the eyes of the public.

Judgment in politics is everything, and this long, drawn-out controversy has dealt a serious blow to that of the Tory leader.

After the omnishambles of the Budget and the fiasco of the West Coast Main Line franchise, this week we had the "combishambles" of the energy row. And if class was the undercurrent to "plebgate", yesterday we had an untimely echo with George Osborne being caught with a standard-class rail ticket in a first-class compartment. A supposed initial reluctance to cough up the extra £190 was later replaced with an insistence the Chancellor was happy to pay.

Of course, all governments make mistakes; it's part of being in charge. However, what a government cannot afford is to appear serially incompetent, because the public at some point will begin to see a pattern and feel the mismanagement is starting to affect their daily lives.

We are only half way through this parliament. If there are more cock-ups, the PM will begin to get a reputation for running a dysfunctional Clouseau-style Government.

If Mr Cameron and the Coalition do not get a grip and fast, it won't be only Mr Mitchell who ends up as toast.