With each day that passes while Jim Murphy clings to the leadership, the last drops of credibility trickle from the remains of Labour in Scotland.

This is no longer a private matter. Where Mr Murphy is concerned, you can take your pick: national joke, or national embarrassment?

I would say that, no doubt, but contrasts are striking. Ed Miliband suffers a historically awful defeat and is gone within hours. Whether his reasons are personal or political, Chuku Umunna decides a contest is not for him. If a candidacy announced on a Tuesday and ended on Friday speaks volumes, what could anyone say, even politely, about Mr Murphy?

Mr Miliband quit with a dignified speech. Opaque as it was, Mr Umunna's statement was hardly an expression of self-interest. Meanwhile, Mr Murphy organises letters of support and scurries around Holyrood in an effort to drum up conscripts ahead of today's Scottish national executive meeting. The fate of one skin is his only interest.

There are 39 former Westminster colleagues who are entitled to wonder about that. Most knew they were done for before May 7. A handful - perhaps even 10, so the story went - pinned their hopes on the rainmaker from East Renfrewshire and strategic geniuses with grand schemes in their carpet bags. That there is still a leadership issue nine days after the loss of 40 seats from 41 says everything about Scottish Labour and its traumas.

Plenty of excuses have been made for Mr Murphy, generally by those who once said he was just the ticket in the sorting-out-Scotland game. You hear, chiefly, that his was an impossible task. No one, say his remaining backers, could have saved Labour here in just five months. There's truth in that, but it is a truth entirely beside the point.

Labour was on the winning side in the referendum. Labour in Scotland, collectively, was very pleased. The Yes movement, wilfully confused at every turn with the SNP, was supposed to be back in its box thanks to a result mistaken for decisive. The caricature Team Murphy called Glasgow Man - a piece of shorthand that said it all - was supposed to trek homewards, think again, vote Labour, and blunt the Nationalists' appeal.

That went well. In reality, Mr Miliband's campaign went very badly and Mr Murphy's stupefying solo effort broke all the records. He took a bad situation and turned it into a catastrophe from which his party in Scotland might never recover. His fans will tell you, even now, about all the energy and effort he put into the fight. A headless chicken has plenty of vim until it keels over.

The Murphy campaign was a mess. It changed tack so often it went around in circles. Themes, so called, came and went on an almost daily basis as though someone was stabbing at some virtual control panel trying to find the button that would work. There was, as usual, no lack of media support. There was no compunction on the candidate's part about political misrepresentation. But if Labour in Scotland is still capable of thought, think about this: voters saw through it all.

That counts, you might have thought, as an excellent reason for the party to be rid of Mr Murphy. Voters are immune to his charms. Losses on the scale suffered by Labour suggest, in fact, an aversion. Half of those who voted did not just reject Mr Miliband (though reject him they did), or succumb to the SNP's mass hypnosis (a piece of desperate nonsense). They scorned what Mr Murphy was selling. They chased him.

In a normal party, that would count as a leadership issue. The fact that Mr Murphy is still around, albeit coming and going by the back door, reminds us that there is nothing remotely normal about Labour now, in Scotland or elsewhere. Mr Umunna's backers in the "Back to 1997!" Blairite crowd might be in mourning this morning. Lord Mandelson will have to look elsewhere for a protege. But amid another tale from the Westminster village, no one has paused to ask about the appeal, if any, of the shadow business secretary to voters in Scotland.

This is not a criticism, per se, of Mr Umunna. None of the remaining candidates for the UK Labour leadership looks or sounds as if he or she has a clue about the Scottish problem, or what it implies. Some, such as Yvette Cooper, seem hazy about the existence of a problem. The entire list of candidates is composed of people who want it known that they might win England back for the party. Good for them.

Len McCluskey, general secretary of the United union, has put an enthusiastic boot into Mr Murphy. That has more to do with the settling of scores - from the file marked "Falkirk candidate selection" - than any proper analysis of what has happened in Scotland and what it means. Mr Murphy certainly led a party to destruction. He did not cost Mr Miliband the entire election, as a simple sum demonstrates. Ed, like Jim, was bereft of appeal. And that "anti-Scottish backlash" is one for rational Unionists to contemplate in the small hours.

By the autumn, Labour will have picked a UK leader with no interest in Scotland beyond traditional vote-harvesting. The Scottish branch will meanwhile have decided whether to add another failed leader to the pile. Still more "listening and learning" is in store. The evidence says Scottish Labour will be no closer to grasping why it was rejected utterly last week. North or south, it will waste its energies fighting over scraps of authority and ignoring what is fundamental.

For Labour, the break-up of Britain has already happened. Toy with the binary cliches of social attitudes surveys to your heart's content: Scotland voted for a programme, a very modest programme, to end austerity and dispense with nuclear weapons. A decisive minority in England preferred a party promising unspecified cuts in social security. As though to emphasise the point, 3.9 million gave their support to nativist animosity and Ukip.

Two countries. Anyone who still denies it needs to get out of London. Once might do. One Labour Party can barely grasp the differences within England, far less the gulf that exists between Scotland and its neighbour. The other wing is in an existential crisis precisely because it cannot decide whether it is Scottish, British, or somehow a bit of both.

Showing Mr Murphy the door will not resolve this. Giving the UK job to Andy Burnham because he's "northern" will not mend the fabric. England is a country that tends towards the Conservatives; Scotland is not. UK Labour's next leader will attend to the first fact before the second.

In these parts, we need a party of opposition. The Scottish Tories continue to fade. The LibDems are one election away from an extinction event. The Scottish Greens, with the best will in the world, have a mountain of list votes still to climb. Once Labour has rid itself of Mr Murphy, therefore, it will have a simple choice.

Just how hard does it need to bite the bullet before it declares its independence?