Jon Craig, Chief Political Correspondent

Jeremy Corbyn has ended 2016 in a row with Barack Obama about Labour's lurch to the left under his leadership.

But after his "Baracking" by the outgoing President, will Mr Corbyn still be Labour leader at the end of 2017?

His enemies in the party hope not. And it appears that even his closest allies fear he might not be.

Winning re-election in 2016, after a botched coup and then a limp challenge from Owen Smith, was the easy bit. With 62% of the vote to Mr Smith's 38%, Mr Corbyn even won a bigger mandate than a year earlier.


But 2017 presents much tougher challenges for the Labour leader if he is to survive. And his enemies are more determined and better organised this time.

'We're beginning to look irrelevant,' a Labour MP in a marginal seat told me. 'We don't have a clear policy on Brexit, or anything else for that matter. People want to know what we'd do if we were in government.'

Critical to Mr Corbyn's survival is the election in the early part of 2017 for general secretary of Britain's biggest union, Unite, which gives the Labour Party £1.5m a year.

It is a battle not just for the soul of the Labour Party, but - according to many of its MPs - for its future as a potential party of government rather than a party of protest.

Mr Corbyn's chief union cheerleader and protector, Len McCluskey, has taken a gamble which may backfire badly for him - and for Mr Corbyn - by bringing forward his bid for re-election.

"Red Len" is being challenged by Gerard Coyne, the union's West Midlands regional secretary, who is backed by a powerful group of Labour MPs, including deputy leader Tom Watson.

The bitter falling out of Mr McCluskey and Mr Watson, who years back used to share a flat together, has been spectacular and looks set to become even more poisonous in 2017.

When I asked Mr McCluskey why they had fallen out, he told me it was because Labour's deputy leader called off peace talks he had set up between Mr Corbyn and rebel MPs.

Mr Watson's friends see it differently. "It was a choice between friendship and saving the Labour Party," a senior Labour MP told me. "And Tom was always going to put saving the Labour Party first."

Image: 'Red Len' McCluskey is taking a big gamble by bringing forward his re-election bid

The campaign to oust Mr McCluskey - Mr Corbyn's "puppet master", according to Mr Coyne - is aimed at smashing Unite's support for the Labour leader and the union's grip on the party's national executive.

Union veterans predict the McCluskey gamble of bringing forward his re-election bid so it now coincides with elections to the union's executive will massively raise the profile of those elections.

"Members of the executive won't like that," one renowned union fixer told me.

"They've always relied on the elections being held very quietly with little publicity and a low turnout.

"They won't take too kindly to Len raising the profile of these elections. They're now going to be the most high-profile set of trade union elections we've ever seen."

For Labour MPs backing Mr Coyne, their long-term game plan - which a leading Coyne backer insists is "doable" - goes like this:

1. Defeat Mr McCluskey and put a moderate general secretary back in charge of the union;

2. Win back control of Labour's national executive from McCluskey supporters and Corbyn backers;

3. Change Labour's leadership election rules back to the old electoral college system of one third of the votes for MPs and MEPs, a third for party members and a third for the unions.

Image: Len McCluskey's rival, Gerard Coyne, is backed by a powerful group of Labour MPs

An ambitious goal? Certainly. Mr McCluskey, 66, is a wily and experienced campaigner.

"With age comes experience," he told me with a knowing smile recently.

But the Unite election is not Mr Corbyn's only critical ballot box test in 2017.

For a start, most Labour MPs are full of gloom about the local elections in May.

At the same time, assuming Andy Burnham becomes mayor of Greater Manchester, there will be a tricky by-election in Leigh, where UKIP's new leader Paul Nuttall is considering standing.

But the real tipping point for the beleaguered Labour leader could be a potentially disastrous by-election in Copeland, after Corbyn critic Jamie Reed announced he is quitting to work for the Sellafield nuclear plant.

Defending a slender majority of just 2,500 in chilly Cumbria, Labour backbenchers fear another torrid by-election after a lost deposit in Richmond Park and fourth place in Sleaford & North Hykeham.

"We're beginning to look irrelevant," a Labour MP in a marginal seat told me. "We don't have a clear policy on Brexit, or anything else for that matter. People want to know what we'd do if we were in government."

Besides Brexit confusion in a constituency that voted Leave, Labour MPs also worry about their leader's stance on both civil nuclear power and Trident submarines, built at nearby Barrow.

Image: Many Labour MPs in marginal seats are nervous

Not to worry, Mr Corbyn. At least your loyal allies are behind you. Or are they?

Two of his most loyal supporters appear to have set a deadline for Labour's fortunes to improve.

Shortly before Christmas, after a YouGov survey suggested Labour had hit a seven-year poll low, sinking to only 25% and 17 points behind the Conservatives, Diane Abbott was asked on TV when the Labour revival needs to happen.

"Within the coming 12 months," she replied candidly.

Only hours later, in another TV interview, former London mayor Ken Livingstone said: "If in a year's time it's still as bad as this, I think we would all be worried."

According to his friends, Mr Corbyn shows no sign of being worried, however.

"His team all think he's doing really well," one of the leader's fellow London Labour MPs told me.

And responding to President Obama's end-of-year criticism, Mr Corbyn's spokesman said the Labour leader "stands for what most people want".

By this time next year, we'll know whether that claim is correct - or whether what most people want is a different Labour leader.

Sky Views is a series of comment pieces by Sky News editors and correspondents, published every morning.

Previously on Sky Views: Tom Cheshire - The internet got what was coming