JUST months ago Richard Leonard was insisting he would lead Scottish Labour into the Holyrood election this year after seeing off a botched coup by a group of his MSPs, so what – journalists and politicians were asking last night – suddenly changed his mind?

Senior party insiders were taken by surprise by his decision and said they had no idea Leonard was going to resign after surviving the rebellion, led by MSP James Kelly, last September.

“This has completely come out of the blue,” one source told The National.

“He always insisted he would stay on as leader until the 2021 Scottish Parliament election.”

So was it, for instance, his opposition to Boris Johnson’s Brexit deal - backed by UK party leader Sir Keir Starmer in the Commons - which prompted his demise?

There was also talk last night that Starmer, or those around him, would have had a role in Leonard’s decision to quit.

“It is inconceivable that Starmer or those close to him would have been involved in this decision,” one insider told The National.

READ MORE: Scottish Labour in crisis as Richard Leonard quits before key Holyrood poll

One report last night said Starmer was furious after Scottish Labour issued a press release on December 30 announcing the party would oppose the Brexit deal at Holyrood because of the economic damage it would cause, and then voted alongside the SNP, Scottish Greens and LibDems against it.

That directly contradicted Starmer’s decision to back the UK Government’s deal.

But other figures insisted it was the persistent and bitter infighting within the party which was the last straw for Leonard.

READ MORE: Here are five of Richard Leonard's worst gaffes as he quits as Labour leader

Neil Findlay, an MSP on the left of the party who is close to Leonard, yesterday said: “Looks like those who have led a three year campaign of briefings to journalists, leaks of private conversations and the constant feeding of stories to the media to bring down a decent and honest man have succeeded. These flinching cowards and sneering traitors make me sick.”

A source on the Labour left agreed with Findlay’s assessment.

He told us: “I can only think that Richard has got totally sick of the internecine warfare that’s going on in the parliament within the Labour group. There has been a constant barrage of leaks to the media which made his life as leader very difficult. If you’re own side is stabbing you in the back, there’s a point at which you just don’t want to carry on and you think enough’s enough.”

But others took a different view, welcoming Leonard’s decision to go and pointing to poor electoral performances in 2019’s European election and General Election. At the former it saw its support crumble, losing both its seats, while the latter saw it lose six of its seven MPs.

On top of the dire election performances, Leonard's decision to resign followed prolonged speculation over his leadership and continuing poor opinion poll ratings for his party.

A Savanta ComRes poll, published yesterday, showed Labour voters switching to the SNP based on the Scottish Government’s response to the pandemic.

The survey – the 18th in a row to record majority support for independence – found more than a third of 2019 Labour voters were more likely to vote for the SNP in what is expected to be an historic election in May with the SNP 35 percentage points ahead of Labour in the constituency vote.

READ MORE: Richard Leonard faces coup as MSPs plot to oust him

“I think it was the right decision for Richard to go. He made no impact in recent months. He should have gone after the General Election in 2019. He wasn’t really a leader,” said one insider.

In a statement, Leonard attacked both the Scottish and UK governments for “mishandling” the Covid crisis and said speculation over his position as leader had become a distraction to the party's ability to get its message across.

“I have thought long and hard over the Christmas period about what this crisis means, and the approach Scottish Labour takes to help tackle it,” he said. “I have also considered what the speculation about my leadership does to our ability to get Labour’s message across. This has become a distraction.”