2020 Games hosts to be announced
A new Olympic host city will be elected later on Saturday with all three candidates facing a challenge to overcome negative issues associated with their bids.
The contest for the 2020 Games is viewed by most observers as a two-horse race between Madrid and Tokyo, with the third candidate Istanbul's best hope being that it survives into the second round of voting.
Both Tokyo and Madrid are pledging to spend a fraction of the cost of the London 2012 Games if they are successful.
The two cities and the third will learn the outcome of the vote when the 100-plus International Olympic Committee members meet for its 125th session in Buenos Aires.
Financial concerns have become the background to this race, especially with worries over the 2016 Olympics in Rio de Janeiro and next year's winter Games in Sochi being the most expensive ever.
Madrid 2020 boasts 80 per cent of its venues are already in place and a construction budget of just £1.3billion - London's comparable cost was £9billion.
Madrid mayor Ana Botella said: "We believe that having a responsible budget represents the new way to understand the Games.
"It's a new model to organise the Games at a time marked by political and economic turbulence around the world."
Istanbul, for a long time the front-runner in this race, has suffered a series of blows in recent months - beginning with the political protests in the city earlier this summer, some of them on proposed Olympic venues, followed by a doping scandal, the jailing of political opponents and journalists, and now the looming war in neighbouring Syria.
Istanbul had had almost the perfect sales pitch until then, talking of the first Games in a predominantly Muslim country and a meeting of east and west.
Its bid team has now taken a leaf out of London's book and will have 50 young ambassadors from sporting backgrounds as part of its final presentation.
Bid leader Hasan Arat insists the city's unique attractions can still win the day.
He said: "Istanbul 2020 will be held against the backdrop of one of the most magical cities on the planet: A bridge between continents, cultures and generations for thousands of years."
As for Tokyo, in many people's minds they are the safe pair of hands that the Olympics needs - Madrid may be a cheap option but the Spanish economy is in dire straits.
Tokyo is also offering a compact low-cost Games with construction costs of around £3billion, and with the security of a strong economy.
It too has issues to overcome, not least the radioactive leaks at the crippled Fukushima nuclear plant.
Hiroshi Hase, a former Olympic wrestler and member of the Japanese parliament, tried to deal with the issue, saying: "There is a very limited area where contaminated water is leaking out in the port. But we will monitor it, remove it and contain it. That is the gist of the strategy."