How Jeremy Corbyn could become prime minister

There is pretty much of a consensus among Labour MPs, party activists who date from before 2015 and commentators that this week's Labour Party Conference is a sideshow.

A sideshow to the big question: 'Who Governs Britain?' because they reckon that Labour under Jeremy Corbyn cannot win a general election.

He is, they say, transforming Labour from a party of power into a protest movement.

:: Nearly half Labour backers 'think party can't win'

Tellingly, even the most enthusiastic Corbyn supporters talk more about changing Labour Party democracy by mobilising a mass movement than about getting a majority of MPs at a general election.

The opinion polls are dire for wannabe prime minister Corbyn. The Conservative lead over Labour is now in double figures and ratings for Mr Corbyn for competence or potential prime minister have plunged to new depths of negativity.

However, from the choice of Mr Corbyn (twice) and Donald Trump to lead a major party to the Brexit vote, surprises and upsets are happening more often.

Here are five factors which could lead to Jeremy Corbyn locking his bike to the railings of Number 10 some time in 2020.

1) Oppositions don't win elections, governments lose them

Theresa May has lot on her plate.

Brexit split the country and it's going to take most of her government's energy to work out what it means, let alone to secure the deals on the economy and migration the UK wants.

Even Brexiteers admit that the economy is slowing down in the short term.

Austerity-lite still means more cuts. The NHS and welfare systems are creaking.

Tory splits are just below the surface and it's far from clear that this government is capable of coming up with the answers.

The Conservatives will have been in for a decade by 2020. 'Time for a change' sometimes beats 'better the devil we know'.

2) The Labour Brand is worth a lot

That's why there hasn't been a split.

In spite of the civil war in Labour and the rejection of Corbyn by most of the party's senior figures, Labour still stands in second place in most opinion polls, close to a 30% share.

It is holding its own in council by-elections and still controls local government in almost of all of England's major cities (including the London mayoralty). Labour rode out the split in the 1980s, it's the Liberal Democrats who have almost disappeared.

3) Corbyn and Labour could be on to something

A lot of people think conventional politicians have had their chance and have messed it up.

Trump, Bernie Sanders, Podemos, Momentum, Front National, 5 Star Movement, UKIP - populist anti-politics-as-usual movements have been gaining ground across the Western democratic world both from the left and from the right, though Syriza in Greece is the only one to make it into national power.

If Corbyn's Labour can harness populist campaigners to its well-entrenched party machine it will be formidable indeed.

They may be a self-selecting minority but Jeremy's "clicktivists" are by far the most successful exploiters of new media we've yet seen in UK politics. (Scotland's Yes campaigners were pretty good too.)

4) The SNP could help him to power

Jeremy Corbyn and Nicola Sturgeon both say they'd never form a pact.

But with Labour out for the count in Scotland, it's pretty obvious that Corbyn's Labour would only be able to command a majority in the Commons with the support or passive acquiescence of SNP MPs.

Whereas the shadow of a deal with Alex Salmond was a liability for Ed Miliband, the prospect of a steadying hand from the popular Mrs Sturgeon might be a reassurance for some English voters - especially if, temporarily, she put on ice the tricky question of another independence referendum.

5) Everybody likes Jezza

With his allotment, geography master's wardrobe and cycling helmet, Jeremy Corbyn is as British as Bake Off.

In person he is usually non-threatening and polite. He has the negative capability of making his radical ideology sound very boring.

If he sticks to the script he's given and keeps cheerful that could be worth a lot of votes, just ask John Major.

I'm not saying prime minster Corbyn is going to happen but it could!