"SCOTLAND voted Labour last night. Just yellow Labour." That, at least, was how one demoralised Labour activist summed up the rout. After months spent knocking on doors, delivering leaflets and talking to people night after night, he did not go along the count, where he would have seen his candidate lose by nearly 20,000 votes. He couldn't even face staying up to watch events unfold on television. Having chatted to so many voters he had a fair idea that six out of 10 were going to place their cross next to the SNP logo. He was disappointed and resigned but mainly he was frustrated.

That was a common reaction among Labour folk. As the SNP's army of activists earned the right to pause, let their extraordinary victory sink in and celebrate, Scottish Labour was again plunged into agonies of introspection. The home truths are as painful as you would expect.

Activists found their manifesto went down well on the doorsteps, something that was also borne out by an Ipsos MORI/BBC Scotland poll during the campaign, which found that in a blind tasting of policies, people liked a lot of Labour's ideas. But the good news ended there.

Huge sections of the public simply did not trust Labour to deliver its pledges. Indeed, they didn't trust Labour full stop.

"It's been clear since last November that people do not trust us or believe us," my chum said, as he prepared to drown his sorrows.

"Another thing we heard all the time on the doorsteps was that Labour is not longer the party it used to be, that we've lost a sense of our roots. It's a message the SNP has used skilfully and people have bought it.

"We are seen as lying, deceitful and untrustworthy. If you press people, they are not sure exactly why that is but they are convinced it's true.

"But whether it is deserved is immaterial, I don't know how we'll get that trust back. I don't know if we'll ever get it back. "There is no-one in the party in my view who could even begin to make a dent in it."

As well as the vague but powerful narrative that Labour is rotten to core, the party has also suffered from the SNP's success in portraying itself as a more radical force, despite a distinct lack of evidence to support it.

"We dismissed these ideas as ridiculous," the activist said. "But they have entered the Scottish psyche. When people voted for the SNP, they believed they were voting for the Labour party."

There was more to Labour's collapse than its abject failure to stop its opponents blackening its name.

By my chum's reckoning a third of the population worships the ground on the which Nicola Sturgeon walks. As for the rest, they just really, really like her. ("She deserves it," he added with surprising enthusiasm. "She's played a blinder.") Ed Miliband, on the other hand, proved a big turn-off for voters in Scotland. The SNP's promise to "stand up for Scotland" and "make Scotland's voice heard" was a major vote winner, even if people were not quite sure what it meant or what they wanted Scotland's voice to say. The SNP's campaign was "immaculate," the activist groaned lastly. His own party's was "a shambles".

The SNP's own analysis of its success is strikingly similar. As the votes came in and the extent of the Nationalists' extraordinary victory became clear, a strategist explained it like this. Voters warmed to the notion of a stronger voice for Scotland, he said, and welcomed the prospect - unrealised in the end - of the SNP supporting a Labour government but making it "bolder and better".

By promising to "end austerity" the SNP came across as more radical than Labour, even though the two parties' economic plans were almost identical.

Ms Sturgeon's leadership was also a big factor. After years in the shadow of Alex Salmond, the SNP leader has emerged as a figure who enjoys broader appeal than her predecessor, especially among women.

A third factor was the SNP's large membership. An army of 30,000 volunteers, nearly one in three members, helped get the vote out on polling day, an effort Labour could not begin to match.

Both parties understand what happened in one of the most dramatic elections Scotland has ever seen. They will take what they have learned into the next Holyrood poll year from now. As things stand, it's hard to imagine anything but a repeat of Thursday night.