It seems like an age since Jeremy Corbyn toured the country, desperately trying to persuade people who already agreed with him to agree with him. It succeeded and those people re-elected him leader of the Labour Party. That age was barely six months ago and now those very same supporters, who were more like fans, are now realising the game is up. It’s not that the friend of the Provisional IRA, Hamas, Hezbollah, Iran and Russia has changed his tune on anything. It’s that slowly but surely, people have realised Corbyn is not up to the job. And soon he will have to go.

In 2015, Corbyn became the voice of change in Labour. Here was an elderly, bearded man who was different from conventional politics. What you saw was what you got, a man of principle, telling it like it is and completely unspun. But as the saying goes, you can fool some of the people some of the time, but you can’t fool all of the people all the time. The game’s up.

There was never anything new about Jeremy Corbyn who was never anything other than another career politician, albeit a not particularly ambitious one. His views were almost identical to those of his great hero Tony Benn who in the 1980s took Labour to the brink of destruction. After a disastrous 18 months in the job, Corbyn has managed to do exactly the same thing.

People were never going to buy into some aspects of his political positions. The public is not, by and large, in favour of unilateral nuclear disarmament, especially now with Donald Trump in the White House, cosying up to Vladimir Putin, the KGB thug in charge of Russia. They are horrified with Corbyn’s associations with terrorists. But above all, they have managed to work out he is not up to the job as leader.

Watching PMQs, observing his bungling behaviour over Brexit, constantly ignoring Labour policies, never holding Tory ministers to account, being AWOL when major issues are ongoing, never speaking to anyone other than those who already agree with him – the list is endless. It is not just me, a seasoned political cynic, who can see this: your ordinary punter can too, without needing the Sun or Mail to help them make up their minds.

Thew wrong Miliband steered Labour onto the rocks in 2015 when his muddled, incoherent manifesto saw Labour badly defeated but those days now feel like a high point for the People’s Party. Corbyn rode into town bereft of any policies at all and has taken the party to record lows in the polls. For Labour, the polls are irretrievable, I suspect even when and if Corbyn quits.

The two coming by-elections are critical to his survival. Copeland and Stoke should be easy wins for Labour but neither will be and the latter is key to everything. if Labour wins, despite Corbyn not because of him, then it will buy him some time. Lose to Ukip’s leader Paul Nuttall and everything changes. This is for both Labour and Ukip, the final throw of the dice. Neither party might recover if they lose, Ukip will gain colossal strength for the future.

Corbyn and his team know all this. Privately they know their leader is hopeless but they dare not say so. A man whose only other serious position of responsibility was in the 1970s when he was chair of the Haringey Council’s housing department was never going to morph into a candidate for prime minister whatever spin was put into effect. And now there is nothing for Corbyn to hang on for except for power itself. And then, only the power to lead a political party that has no chance of forming the next government and possibly the couple after that.

Worse still, Corbyn and his team don’t care that they cannot win the next election. Their raison de’tre is not to win elections but to build a social movement. They cannot imagine a compromise with the electorate to appeal to voters other than those on the far left. Tony Blair’s winning rainbow coalition was a sell out, according to the comrades. The problem with their argument is that at three general elections, the electorate liked what they saw.

It is time for Corbyn to go and Labour must elect a candidate of the centre left who can unite the party and build for the next general election, with a view to minimising the damage that 18 months of Corbyn has caused. It is extremely unlikely Labour could win in 2020 but there is one hope you can cling to: events. If a week is a long time in politics, what’s over three years? Theresa May appears to be the least equipped person to be prime minister in my lifetime and is hopelessly out of her depth and she will spend the next two years grappling with a complex and messy process of leaving the EU, which will use most of her time and resources. Add an unseen economic collapse, terrorist attacks, a disastrous military conflict involving Trump and/or Putin, natural disasters or any number of unforeseen calamities and governments can be rocked. That is why Labour must get shot of Corbyn, skip a generation and elect a younger leader and give her, or him, the chance to build the party in their image. Not a populist party, but a popular party that speaks for everyone.

It’s about far more than the future of Labour, although anyone from a leftist position must surely be mortified by the country’s huge lurch to the right with the Brexit vote, the dangerous dalliance with the unstable Trump in Washington and Putin in the Kremlin rubbing their hands in expectation of economic and political destabilisation in Europe and the huge uncertainty we face.

Every Labour MP who voted for May’s hard Brexit, apart from the tracherous Hoey and Stuart et al, did so in the sure knowledge they were voting to make the British people poorer and that they were voting against Labour’s official policy on the EU. Many MPs, including the ludicrous Diane Abbott, admitted they were voting to make people poorer. And the man who led them through the lobbies was the great socialist himself, Jeremy Corbyn. Some socialist.

If Corbyn really does care about the poor, the sick, the disadvantaged, the homeless, the NHS and our schools, he should resign now. If he puts his own ego first, preferring to preach his vague rhetoric for what will become a declining cult following, Labour will never forgive him.