SO much has befallen Labour in 2015 that it takes a real mental effort to remember when Ed Miliband was seriously touted as Prime Minister.

Can it really be less than 12 months since the Conservatives feared being ejected from office and replaced by an uneasy Labour-SNP pact? Less than a year since Jim Murphy predicted he would hold all 41 Scottish seats?

Less than a year since no-one had heard of Jeremy Corbyn?

What crazy, distant days they seem now, our heads shaking in collective disbelief.

Yet there was a time, let’s call it January, when 2015 looked pretty good for Miliband. Back then, most polls had Labour either neck and neck with the Tories or slightly ahead, pointing to a second hung parliament.

A few days into the new year, he launched Labour’s election campaign in Salford with a message of “hope, not falsehood” and a promise to cut the deficit and balance the books.

The speech evidently didn’t cut much ice north of the border. Over the following weeks, the Tory peer Lord Ashcroft ran polls in 16 Scottish seats, and when the results dropped in February, they were stunning.

The wave of support the SNP had ridden since the referendum now threatened to wash away Scottish Labour.

Six of Labour’s seven seats in Glasgow were forecast as SNP gains. Name recognition was no defence.

In Inverness, Danny Alexander, the LibDem Chief Secretary to the Treasury, was well behind the SNP, as was Labour’s UK election co-ordinator, Douglas Alexander, in Paisley.

The figures were so awful for Labour, they were treated were a degree of scepticism.

With three months to go, surely Labour could pull something back? Even Ashcroft felt obliged to note: “With a vigorous Labour campaign there remains room for movement before May.”

Alas for Scottish Labour, it didn’t get a vigorous campaign, it got Jim Murphy.

To be fair, it’s unlikely anyone could have halted Scottish Labour’s decline by the election.

After decades of being sustained by loyalty and habit, rather than enthusiasm or merit, the party had thrown away the last of its goodwill by joining the Tories in Better Together.

But Murphy, the unrepentant Blairite elected Scottish leader in December 2014, was never going to kickstart the recovery, especially with his high-energy, low-impact campaigning style.

Instead of considered policies, Murphy offering patronising gimmicks, spewing out random ideas while talking interminably in soccer metaphors.

Sometimes, he even managed to weave the two strands together, prioritising the reintroduction of booze to football grounds. The polls duly got worse.

By March, he publicly admitted they were “bloody awful for Scottish Labour”.

Yet south of the Border, Miliband was still seen to have a chance.

He survived his cheesy, “Hell, yes, I’m tough enough”, soundbite to Jeremy Paxman.

While on social media #Milifandom broke out, as hundreds of Labour students – sorry, real people – photoshopped his head onto the ripped celebrity torsos.

But with the televised debates in April, the wheels started to come off the Labour jalopy. Miliband visibly failed to connect with audiences, and was fully eclipsed by Nicola Sturgeon.

His prep notes for one debate, left in a TV dressing room, showed he wanted to become a “happy warrior”, while in another debate, he literally stumbled off stage at the end.

Small things in themselves, but suggestive of someone ill-at-ease, psyching themselves up, unconvinced of their own future, something instinctively grasped by voters at home.

Miliband’s weakness as a leader and Sturgeon’s strength was also exploited by Tory election strategists to warn of a Labour government blackmailed by an insatiable SNP.

An economy derailed, Trident cancelled, UK plc in chaos – the messages didn’t depend on English voters disliking the SNP to work, they just had to doubt Miliband, and they did.

By late April, another Ashcroft poll said Murphy would lose his East Renfrewshire seat.

Then, just when you thought it couldn’t get worse, out lurched the Ed Stone, an eight-foot limestone slab inscribed with pledges, earmarked for Miliband’s new-look Downing Street.

“This isn't just measuring the curtains, this is something on a Biblical scale. It reminds me of the 10 Commandments,” said Tory chairman Grant Shapps.

May 7 suggested another Commandment might be handy: Thou shalt not believe the polls. Though Ashcroft had been vindicated, most pollsters were way off the UK result. As Big Ben chimed at 10pm, the BBC exit poll put the Tories clearly in front.

It was one of the biggest shocks of the political year.

Lord Ashdown, the former LibDem leader, promised to eat his hat if it was right. But its truth was soon confirmed as the Tories held on to a series of low-hanging marginals that Labour needed to win, and even claimed the scalp of shadow chancellor Ed Balls.

Overall, the Tories won 36.9 per cent of the vote, Labour 30.4 per cent.

Both parties actually increased vote share, Labour by most, yet Miliband lost 26 seats while the Tories gained 24, giving David Cameron a surprise 12-seat majority.

However the most dramatic numbers were those of the LibDems and SNP. Having entered the election with 57 seats, Nick Clegg exited with eight, his party’s vote down from 23.1 to a fringe 7.9 per cent. The SNP added an extraordinary 50 seats to their previous six on a 50 per cent vote share.

Helped by tactical Tories and LibDems, Labour held a single Scottish seat, Edinburgh South. The party “had gone from Red Clydeside to Red Morningside”, quipped the SSP’s Colin Fox.

As Ashcroft predicted, Murphy and the Alexanders were roadkill. Glasgow North East, that glimmer of hope for Labour, saw a mind-boggling swing to the SNP of 39.4 per cent.

It was a generational break. Habit, Scottish Labour’s old fallback, no longer worked. Years of uninspiring leadership, infighting and complacency, compounded by disaffection over Iraq and the referendum, had finally proved too much for electors.

Scottish Labour was punished to within an inch of its life.

Miliband, like Clegg and (briefly) Ukip’s Nigel Farage, resigned the next day. Murphy limped on gracelessly for another month, insisting he could stay before finally conceding he couldn’t.

But Labour’s tumble down the rabbit hole didn’t stop there. If anything, it became curiouser and curiouser, starting with the contest to replace Miliband.

At a meeting of left-wing MPs, John McDonnell and Diane Abbott refused to stand as the left’s token candidate and told Jeremy Corbyn it was his turn. “Go on then,” he replied.

And so began the most significant Labour leadership contest since Tony Blair in 1994.

After only just scraping into the race, Corbyn went stratospheric, not least because his rivals – Yvette Cooper, Andy Burnham and Liz Kendall – were woefully leaden.

With many Labour members as jaded as Labour voters, Corbyn was welcomed as the antidote to Blairism, a return to principle after Iraq and kow-towing to the City.

Never mind that he wasn’t much cop as a speaker, or hadn’t run anything in Labour, or couldn’t price his ideas, or was almost certainly unelectable as PM. The main thing was he was authentic. He spoke his own mind. Hell, he even had a beard.

Backed by the unions and 10s of thousands of new members, the Islington North MP romped home with 59 per cent of the vote; Kendall, the Blairite candidate, got 4 per cent.

Around the same time, Murphy’s old deputy, Kezia Dugdale, took over in Scotland.

Both Corbyn and Dugdale have had mixed starts.

Monstered beyond reason by nearly all of the press, Corbyn struggled with deep splits in his Shadow Cabinet over Trident and Syria, but came through because of the scale of his mandate and a novel, assured approach at Prime Minister’s Questions.

The former serial rebel has also grasped the need for parliamentary discipline, stirring the membership by email to remind internal critics of what's good for them.

Labour’s solid win in the Oldham by-election has quelled talk of a coup – for now. The English council elections look rocky, but Labour is poised to win the London mayoralty.

Meanwhile, the Conservative Party is back to devouring itself over Europe. So Corbyn goes into 2016 in better shape than his fans expected and many of his MPs would have wished.

There is no solace for Dugdale, however. Despite a good conference and some palpable hits over education, as the Holyrood election nears, Labour are squinting at the SNP across a 35-point chasm in the polls.

Another rout could well see the left agitate for Dugdale to be replaced by a Corbynite MSP such as Neil Findlay. Dugdale knows the stakes.

“We may not be at the bottom of where the Labour Party could get to in Scottish public life,” she said presciently when launching her leadership bid in June.

To play down expectations, she uses a Murphy-esque football analogy when asked about May – success would be Scottish Labour “clapped off the pitch at the end of the season”.

It’s a nice line, but a fantasy. You don’t get clapped off if you’re clapped out.