The party trails the Tories by double-digits while Mr Corbyn's approval ratings, weak from the outset, have gone through the floor. Polls suggest that, at the next general election, Labour could sink below the depths plummeted by the Conservatives in 1997.
However, Mr Corbyn's leadership risks not simply political annihilation for his party, but moral catastrophe too.
Nothing illustrates that better than his handling of the issue of antisemitism, a problem which goes to the very heart of his ideology. As Joshua Simons, a former policy adviser to the Labour leader, suggested last week, Mr Corbyn and his staff view Jewish people through a lens shaped by "frenetic anti-imperialism focused on Israel and America". Thus, as Simons also revealed, a senior aide wanted the greeting Chag Kasher VeSameach (which translates as "A happy and kosher holiday",) removed from Mr Corbyn's Passover message, for fear that his supporters might think the use of Hebrew "Zionist".
It has been claimed that the aide was Seamus Milne, Labour's director of strategy and communications, but Labour has denied the incident occurred.
For Mr Corbyn and Mr Milne antisemitism only exists when it is perpetuated by skinhead fascists, hence the Labour leader's frequent references to his mum battling blackshirts on Cable Street.
That is why, despite all that has happened over the past year, Mr Corbyn doggedly continues to add insult to injury.
It is why he stood by in July while one of his supporters accused Jewish MP Ruth Smeeth of conspiring with journalists at the launch of the Chakrabarti report, and then could not bring himself to mention the word "antisemitism" in a statement about the torrent of online abuse to which she was subsequently subjected.
It is why he appeared at a rally earlier this month alongside Jackie Walker, a woman who claimed that Jews were "the chief financiers of the slave trade".
And it is why he plans to headline a Stop the War Coalition conference next month at the head of a rag-tag army of Israel-haters, some of whom have reportedly made clear their sympathy for Hamas.
Many Labour MPs and members who joined the party before Mr Corbyn became leader are appalled and ashamed by such behaviour. But, as his re-election next weekend is likely to show, their views are now a minority within the party.
It is not the small number of antisemites in its ranks who are destroying the Labour party; rather it is the wider lack of outrage at a man who shows total indifference to the problem.
Even when hammered at the polls, as in 1983, the Labour Party has been able to console itself with the words of former leader and prime minister Harold Wilson: that it is a "moral crusade or it is nothing".
Having shredded the party's electoral prospects, Mr Corbyn now threatens to destroy that crusade, too.
