For lovers of the English tongue, there is no greater thrill than being present at the birth of a dramatic linguistic development. I refer here not to the OED’s annual list of newly accepted words. You can see the addition to the lexicon of popular slang words like “hashtag” and “omnishambles” coming.

What I mean is something wholly unforeseeable, if not totes amazeballs, and for the latest contribution to this precious etymological sub-species we give thanks to Harriet Harman. The acting leader of the Opposition this week boosted the ranks of contronyms – words with definitions that diametrically contradict one another.

You’ll be familiar with “cleave” (to stick to and to separate), “sanction” (to allow and to disallow), and of course “literally” (literally; and metaphorically). Thanks to Harriet’s brazen and bewildering attempt to bounce the party into backing George Osborne’s proposal to limit child benefit to two children, the verb “to oppose” may now be defined as: 1) “to oppose”; and 2) “to support”.

Similarly, the parliamentary term “Her Majesty’s Opposition” might now be pithily translated as: “the political living dead who imagine that feigning agreement with the kind of regressive policies they went into politics to fight will somehow ingratiate them with the public”.

The only thing that might prevent Harman being remembered less for her long and impressive career than a single act of folly at its conclusion is that the public isn’t listening. There is nothing she or the Labour leadership contenders could say that would interest anyone but a political hypernerd.

If Liz Kendall regaled a hustings with her plan to make the culling of day-old beagle puppies a Labour manifesto pledge, it would float above the public consciousness. If Andy Burnham unveiled an initiative to scrap the RAF and give all the Typhoon fighter jets to fellow Everton fans in a half-time raffle at Goodison Park, it wouldn’t attract a shrug. If Sound of Music superfan Yvette Cooper declared that her priority, as PM, would be to make the failure to yodel “The Lonely Goatherd” while waiting at bus stops or on suburban railway platforms a statutory offence carrying an automatic 14-year sentence, who would care?

A black hole contest like this distorts time; it may feel like years since the leadership shortlist was first unveiled. It is, in fact, precisely one month – and the only candidate with any momentum is the one who was allowed to make the cut only at the last moment by way of a satirical afterthought.

Like Harman’s take on the duty of an opposition, Jeremy Corbyn’s candidacy presents a glaring paradox. He is by light years the best candidate, in that he actually believes in things and can articulate those beliefs in a way humanoid life forms can understand. He believes that limiting child benefit is wrong, for instance, since it would restrict the life chances of those who most need help to escape entrenched poverty.

Harriet Harman once believed the same. Indeed she might have described it as an irreducible core belief that punishing the poor for being poor is vindictive and counterproductive. Now, her lone belief appears to be that moulding the party into an insipid, comically unconvincing Tory tribute act is the solitary option.

Corbyn’s beliefs, on the other hand, have survived the passage of four decades intact, which is why he is by light years the worst candidate. Those beliefs are noble and sincere, but only about 17 people in this country share his faith in the command economy.

Interviewed on Channel 4 News on Monday, Corbyn dealt splendidly with Krishnan Guru-Murthy, that laureate of preening self-regard, when asked why he once addressed Hamas as his “friends”.

Corbyn, who appreciated the importance of dialogue with the IRA long before that came into vogue, sensibly replied that you have to talk to people you disagree with, and that he used “friends” as a courteous collective term. Such a trivial line of questioning, an impressively raging Corbyn went on, was purely tabloid.

So it was. Guru-Murthy can be a smug twerp, and it was embarrassing to find a serious news programme indulging in babyish, Sun-style hectoring. Yet this is a tabloid world, and the thought of what the Daily Mail would do to Corbyn as Labour leader is too agonising to contemplate.

While the notion that Labour faces an existential crisis has quickly become a cliché, Corbyn’s momentum and Harman’s lunacy suggests it is worse than that. When a woman who spent her entire working life fighting inequality finds herself actively supporting it, this begins to look like a post-existential crisis.

For now at least, the Labour Party has effectively ceased to exist. It is as if that fiscal Dracula George Osborne sucked the lifeblood from its neck with his cunning, cynical Budget, and thus completed the vampirical process.

And so, while Harman flirts with rewriting the opening lines of her obituary, the zombie leadership election plays on to deafening indifference for all but Jeremy Corbyn. In what reminds one of a stultifying dreadful fringe theatre production of a 127th-rate family psychodrama, they let the mad uncle out of the attic as a joke, but found when he came downstairs that he made far more sense than his sneering nieces and nephews.