Three cities vying to host the 2020 Summer Olympics are making their final pitches to the international committee charged with picking the venue for the colossal sporting event.

The International Olympic Committee's 100-odd members will cast their secret ballots this Saturday to choose Madrid, Tokyo or Istanbul as the victor.

But each country is struggling to overcome domestic challenges that range from political unrest to a persistent recession,  threatening to derail their two-year-long campaigns to secure the Olympic and Paralympic Games.

"The various cities are quietly pointing out the deficiencies in the other cities," said noted Olympic historian David Wallechinsky. "While they’re not supposed to do that,... there's always a way."

The bid by Tokyo, a steady bookie favourite over the past months, has been marred by concerns over the inability of Tepco to contain a leak of radioactive water from the Fukushima nuclear plant in northern Japan damaged by the 2011 disaster.

Large scale anti-government demonstrations swept across Turkey in June and the escalating civil war in Syria threatens to spill over into the region.

The low-cost option

For Madrid, it's the country's economic uncertainties that plague its bid to host the costly sporting event. Spain suffers from a crippling 27 per cent jobless rate.

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Spanish Crown Prince Felipe of Asturias was among those seeking to sway the 2020 Olympic Bid Committee to choose Madrid. (Jean-Christophe Bott/Keystone/Associated Press)

"On an economic ground, it’s hard to see how Spain represents a credible bid," says Stefan Szymanski, professor of sport management at the University of Michigan. "Even though it’s seven years away, the Spanish economy is such a terrible mess, is it really worth putting public money into this kind of venture over the next five to six years?"

To counter concerns, the debt-stricken country promises a penny-pinching Olympics that will be "a huge financial boost, which will help to contribute to the economy," the president of the Madrid  Autonomous Region, Ignacio Gonzalez, said as the bid competition got underway.

Spain says 80 per cent of the necessary venues are already built, leaving an estimated $1.9 billion to be spent constructing the remaining buildings. It's the lowest cost bid by far and less than half of the next closest, Japan's estimated $4.4 billion infrastructure budget.  

An IOC technical assessment of the bidding cities found Madrid's proposal feasible, despite the country’s long recession.

And as Wallechinsky notes, "on the positive side, everybody likes being in Spain."

Legacy counts

However, low constructions costs could be interpreted as a disadvantage by an Olympics committee more interested in its own legacy.

"If you have a lot to do, then they will be left behind with a lot of monuments, with a little plaque saying, ‘Built for the IOC Olympics Games in 2020’," noted Szymanski. "If you’ve already got [the buildings], where do the plaques go?"

The Istanbul bid rests largely on its promise of legacy. Turkish Prime Minister Recep Tayyip Erdogan recently made a fervent pitch for Istanbul, touting its "distinction" since it's the only country on the roster that has never hosted the Olympics.

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Protests in Turkey could dissuade the Olympic committee from selecting Istanbul as the venue for the 2020 Games. (Vadim Ghirda/Associated Press)

As such, the country needs to build about 70 per cent of its 38 venues, at an estimated cost of nearly $20 billion.

"There’s a large number of people who would like to see the games being held in Istanbul because it’s in a part of the world that hasn’t held the games before," said Wallechinsky, president of the International Society of Olympic Historians.

But Wallechinsky adds that the huge demonstrations in June don't promote a stable environment and makes voting members on the IOC nervous. 

Another key measure for the IOC is the level of local enthusiasm for the Games — and in that area, Turkey comes out ahead. The committee's own survey found support for the Olympic bid from Istanbul residents  was at 83 per cent. Comparatively, Madrid support sits at 76 per cent.

Japan vows 'drastic measures'

Tokyo struggled from lack of political and public support in its 2016 Olympics bid but it saw rising support this time around. However, with 70 per cent support, it's still the lowest of the three.

Eager to counter the perception of a wary public, the Japanese government conducted its own poll, which found 92 per cent support the Olympic bid.

Japanese Prime Minister Shinzo Abe is fully backing the bid, unlike his predecessor during the prior 2016 bid. He plans to leave the G20 summit in Russia early to help make the final pitch before the IOC in Buenos Aires this weekend.

The Asian country’s proposal says the Olympics will seek to lift the nation’s spirits after the 2011 earthquake and tsunami, but the failure to contain that leak of contaminated water at the Fukushima nuclear plant raises safety concerns. Radiation levels around tanks holding the toxic water reached a new high on Wednesday.

But Abe says he aims to reassure the IOC that the crippled plant in northern Japan won’t pose a danger in seven years.

"We are determined to take drastic measures of a maximum scale so that there are no problems by the 2020 Olympics," Abe told reporters while leaving for the G20 summit in Russia.

Japan has remained a steadfast favourite in the three-way race.

The country has hosted three Olympics in the past, which Wallechinsky notes went "extremely smoothly": the 1964 Summer Olympics and the 1972 and 1998 Winter Olympics.

"The Japanese are kind of a safe bet," said Szymanski. "They can deliver this with their eyes shut."

The final decision may, however, come down to winning the hearts of the voting IOC members.

Last-minute choice

Rio de Janeiro came from behind to win the 2016 Olympics with an attention-grabbing final presentation that used an interactive map to show each city that had hosted the Olympics. As each city lit up, it was clear that the Olympics had never been hosted in South America.

"Then they pointed out that of the nations with the 10 largest economies, Brazil was the only one that had never hosted the Olympics," said Wallechinsky. 

That promise of a legacy caught the IOC's attention. However, protests in Brazil ahead of the country hosting the lavish sporting spectacle plus the World Cup may cause the committee members to hesitate from selecting Istanbul, another untested location.

But if Istanbul wins, it will be the first Olympics held in the Middle East and the first in a predominantly Muslim country

Selection of the next Olympic site may simply come down to political manoeuvring among the more than 100 voting members. Szymanski calls the Spanish "extremely well connected" while the Japanese are astute and well liked.

Or it could rest on a continent-hopping equation. With the two prior Summer Olympics held in Europe and Latin America,Tokyo might be the next logical choice.

Or will Istanbul's status as the only city on two continents help it triumph?

Perhaps most important to remember in all the deliberation about the next host city is the fickle nature of it all.

"This is the most unpredictable electorate on the planet," said Szymanski. "It’s so totally random."