On the one hand they must strive to generate excitement about whichever project they are being paid to help, much as in former bid battles.

On the other they need to highlight how little preparatory work will be required in their particular candidate-city so as to be ready to lay on the mother and father of all sporting festivals in eight and a half years’ time.

A Sebastian Coe-esque peroration about transforming a 50-foot mountain of rotting fridges into an Olympic Aquatics Centre, however inspirational, would be spectacularly out of tune with the new zeitgeist.

Such misplaced eloquence might conjure up in residents’ minds new worries about the cost of what they are potentially signing up for.

Which might in turn lead to nosediving local support levels and revived talk of – gah! – referendums.

And where would that leave us? Quite possibly in the junk-yard with Hamburg’s quietly impressive but abandoned bid, that’s where.

The trouble is if bigging up the transformational nature of a major urban regeneration project is off the table, what do you replace it with?

Scrutiny of this week’s media releases from the two cities generally seen as frontrunners in the four-horse 2024 Olympic and Paralympic race – Los Angeles and Paris – suggests the spinmeisters are still groping towards the requisite new idiom.

The releases coincided with submission to the International Olympic Committee (IOC) of the first part of the candidature file by all four competitors - the two I have mentioned, plus Budapest and Rome.

It is scarcely surprising under these circumstances, but I think revealing nonetheless, that both Paris and LA have gone for the portentous but usefully vague “new era” cliché. (“A new Games for a new era” – LA; “a ‘new era’ Games” – Paris.)

This at least had the positive spin-off of setting me humming the song of a similar title by The Specials, a band from the former car-making stronghold of Coventry in the English Midlands, whose excellence is a reminder of what the human spirit is capable of, even amid crushing urban decay. 

Both cities then go out of their way to highlight not the epic sweep and extraordinary brilliance of their respective plans, but how many of the key ingredients of the Olympic/Paralympic recipe they already possess.

Paris claims “95 per cent of venues already existing or temporary to minimise required investment”.

LA comes up with a new category to exceed even that elevated figure, boasting that “an impressive 97 per cent of Games venues are either already in place, planned by private investors or temporary”.

“Planned by private investors”: code, I suppose, for projects that ought not to hoover up Angelenos’ tax dollars; but which would have to be built nevertheless.

You need to read the releases pretty carefully for it to sink in, but if you do you start to realise that both cities would actually be transforming their fair share of rotting fridges.

The spin requires LA to proclaim itself “an Olympic Games-ready city”, conjuring an image of a plump, stuffed and basted poultry item just waiting to be wrapped in silver foil and popped into that Games-time oven.

Yet the very next line talks of an $88 billion (£61 billion/€79 billion) transportation upgrade programme.

$88 billion! A figure that puts even those Javelin trains and the rest of London’s successful 2012-related transportation upgrade in the shade.

We also learn that existing venues such as the famous Coliseum, Pauley Pavilion and the Rose Bowl will have undergone “significant renovations” by 2024.

Paris’s “new legacy venues” located in its “younger and fast-growing outer ring” include an Aquatics Centre, media village and Games Village, “which together will deliver essential new housing after the Games”.

Gnarled Olympic reporting veterans such as myself might be excused for perceiving certain parallels between this and the scourge of rotting fridges that was the unapologetically ambitious London 2012 project.

Since they are stuck with playing down the impact of the Games blueprints themselves, the spin-doctors have turned to more nebulous matters to inject excitement.

The trouble is that since they have identified very similar sets of buzz-words that they appear to think the IOC will be enthused to hear, they pull off the not inconsiderable feat of contriving to make these deeply contrasting cities – I mean how much, really, do LA and Paris have in common? - sound almost interchangeable.

You might just about guess that “a city of romance, creativity, innovation and fun” refers to Paris and “a hub of global entertainment and innovation” to LA. Just about.

But what about these four?

a) An “unparalleled culture of creativity and youthful energy”;

b) A “desire to be defined by the future”;

c) A “journey of re-invention to unleash its innovation, radiance and sense of optimism”;

d) A “relentless commitment to progress and imagining what is next”.  

For the record, phrases a and d come from the LA release, with b and c taken from Paris. Or is it the other way around?

To be fair, Los Angeles appears to have concluded that it is still OK to boast about sustainability, envisaging “The first energy positive Olympic and Paralympic Games, powered by the sun.”

Referencing the sun, here and in its angel logo, seems to me a smart idea, since not only is it an element people genuinely associate with Southern California, but it is the source from which the Olympic flame is kindled.

Even this presentational highlight was marred, however, by a bizarre allusion to “more than 4,000 hectares of available roofs for new solar systems” – the sort of language more suited to an energy company’s annual report than a pithy, snappy media release encapsulating an Olympic project’s essential attributes.

The symbolic role of LA’s sun seems to have been taken in the Paris bid by the river Seine, which some might think a questionable strategy, especially given the strength of the French capital’s hand in many other respects, when you are up against, inter alia, the city on the mighty Danube.

For now, we can hold the symbol responsible for the single most preposterous sentence in the two releases, an unhappy marriage of convenience between a flight of poetic fancy and an attempt to tick all the boxes.

“The concept of sport flowing through the Seine, with a ‘river trail’ of live sites and sponsor activation, will,” we are told, “enhance fan engagement and ensure the Seine experience is at the very heartbeat of the Games”.

So, while Agenda 2020 has proved inadequate to head off a dismal year for the international sporting movement, it is posing a real challenge for bid-city spin-doctors and those of us striving to paint an accurate, dispassionate picture of what these four projects would actually entail.

One wonders what the IOC members, whose job it will be next year to select the best project, are going to make of it all.