It can hardly be a coincidence that Theresa May's announcement of a summer general election should coincide with Labour's worst poll showing for nine years. In terms of electoral prospects, the outlook really won't get much better than this for the Prime Minister.

In calling a general election for 8 June, Mrs May must also surely have in mind Gordon Brown's bumbling and catastrophic equivocation over whether to hold a snap election back in the autumn of 2007. The counterfactuals thrown up by a steelier Brown premiership remain fascinating to this day: Labour would almost certainly have enjoyed victory had an election been called; a cherubic and inexperienced David Cameron would have disappeared into deserved obscurity; and austerity would have remained a crackpot idea rumbling around a few right-wing think tanks. Britain might also still be in the European Union, while the Labour Party could still conceivably be in power.

That obviously isn't how things panned out – and Theresa May has very clearly learned something from Brown's ineptitude. A weighty electoral mandate, which seems to be the likely outcome of an impending election, will also aid Mrs May in her forthcoming negotiations with Europe over Brexit.

Yet for anyone with both an interest in the Labour Party and a residual grip on reality, the strongest instinct on hearing today's news must have been a powerful sense of dread. Labour under Jeremy Corbyn is facing an electoral wipe-out worse than anything since 1983 under Michael Foot. I suspect things will turn out far worse than that even, and will look more like 1935, when the party won a mere 154 seats.

Outside of central London, it is doubtful anymore whether there is such thing as a safe Labour seat. The grim irony of Corbyn's short-lived ''movement'' will not be a hopeful leftward shift in the so-called ''Overton window''; it will be a new social consensus built on socially divisive grammar schools, exit from the European Union and the gradual running down of the NHS.

Were Jeremy Corbyn a Marxist rather than a half-baked throwback to the 1960s ''New Left'', he would understand that it is power – rather than good intentions – which shape reality. You change the country by winning over sceptics and enacting a set of policies, not by giving speeches to the converted at protests and rallies.

I suspect things will turn out far worse than that even, and will look more like 1935, when the party won a mere 154 seats.

Perhaps the worst thing about today is the extent to which the country is crying out for both a credible opposition and an alternative that prioritises things like workers' rights and public services. Vapid centrism is a busted flush, as I suspect we might soon learn from France, and has nothing to say to the young care worker changing stoma bags on a zero hours' contract and a pitiful wage, or the communities in South Wales that were forced to inhabit a ''post-work'' world long the subject became a talking point for the Islington chatterati.

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Jeremy Corbyn, speaks at the Scottish Labour Party Spring Conference in Perth, Scotland on 26 February, 2017Reuters

The idea that the left should rally around a leader who may end up discrediting socialist politics for a generation is about as silly as the notion that there was no fundamental difference between Hillary Clinton and Donald Trump. Nor will wish-thinking suffice: one can hope for a Labour victory until the cows come home, but calls for ''unity'' will wash straight over the heads of all who value independent thought over boring party-line sycophancy.

The other essential point is that Theresa May is eminently beatable. Along with the dire Labour polling released last weekend, another poll showed that individual Labour policies score well among the public. Almost three-quarters of voters supported raising the minimum wage to £10 an hour, whereas 60 per cent favoured an increase of the top rate of tax to 50 per cent.

The idea that the left should rally around a leader who may end up discrediting socialist politics for a generation is about as silly as the notion that there was no fundamental difference between Hillary Clinton and Donald Trump

A similar thing was noted two years ago when Ed Miliband led the Labour Party. Yet as we subsequently found out, you can promise to double every voter's annual income and it is no guarantee they will vote for you if they do not believe you have a cat in hell's chance of enacting it.

There is no point sugar-coating Labour's predicament. The public will see June's election as a contest between a steady hand in troubled times and an irritable incompetent. It is a choice between a bossy (and let's be honest, quite mediocre) headmistress or an Albert Steptoe lookalike who still believes Cuba is an aspiration rather than a grim warning. And that is before Conservative central office begins to crank out Corbyn's own words on everything from Venezuela to re-opening the coal mines to Hezbollah.

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Britain's Prime Minister Theresa May prepares to speak to the media outside 10 Downing Street, on 18 April, 2017REUTERS

Jeremy Corbyn has responded to today's announcement of an early election by saying that he "welcomes" Theresa May's decision. That is his prerogative. However it is a luxury derived from a good income and a steady job (Corbyn has been an MP since 1983). Many people in Britain do not enjoy such a degree of comfort and stability. Many rely on food banks to eat and unscrupulous employers for a paltry income in order to scrape by.

The public will see June's election as a contest between a steady hand in troubled times and an irritable incompetent

A good number of these people depend on the existence of Labour governments, not to usher in utopia or end the struggle, but to "bring about a change in its terms", as the great Labour MP and founder of the NHS Aneurin Bevan phrased it. The abstractions of ''socialism'' and ''fully automated luxury communism'' are dwarfed by earthlier and more pressing matters, like getting a GP appointment or finding a full-time job that pays a regular wage.

Events in the coming months will unfold as predictably as the plot of a cheap airport thriller. Labour is heading for its worst election defeat in living memory. Many Britons will pay a terrible price for that.

But the blame for this tragedy will lie not only with the protagonists in government. It will lie too with those who, for reasons of vanity, misplaced idealism and a bundle of delusions they projected onto one man and wrote Labour's suicide note two years ago when they voted for the most incompetent leader in the party's century-long history.