As the weekend vote looms by the International Olympic Committee to decide the city that will host the 2020 Summer Olympics and Paralympics, experts in Japan say the three candidates are neck and neck amid lingering worries about the radioactive water leaking from the Fukushima No. 1 nuclear plant.

They feel the outcome will depend on the final presentation and on whether Tokyo can persuade IOC members the city will provide a model for contributing to the future of sports.

The IOC will choose the host city at its general assembly Saturday in Buenos Aires. Some 100 members will vote by secret ballot at the Hilton Buenos Aires hotel, choosing between Tokyo, Istanbul and Madrid. The experts say all three cities have their strengths and weaknesses.

Istanbul was seen as heavily favored at first, given that it would be the first predominantly Muslim city to host the Summer Olympics, said sports journalist Seijun Ninomiya. However, the fierce civil war in neighboring Syria and anti-government demonstrations at home have sent security concerns through the roof.

Madrid’s strongest point, Ninomiya said, is its compact plan for the event, in which all venues would be situated within 10 km of the Spanish capital’s center. However, possible financial problems caused by Spain’s economic crisis is the city’s primary weakness, he noted.

On Tokyo’s bid, Ninomiya pointed out the city is safe in terms of security and has the experience of hosting the Olympics in 1964, but the persistent radioactive water leaks at Fukushima No. 1 appear to have raised concerns among IOC members.

“To be honest, it’s impossible to predict how it will turn out,” Ninomiya said at an August symposium in Yokohama.

Munehiko Harada, a Waseda University professor on sports marketing, said that while he thinks the race is in a three-way tie, the bookmakers are giving the edge to Japan’s capital.

For example, the British online betting website Coral gives Tokyo the best odds, at 13-8, followed by Madrid at 3-1 and Istanbul at 10-3. Another betting site, Ladbrokes, meanwhile has Tokyo at 13-8 and both Madrid and Istanbul at 3-1.

“There’s an atmosphere that Tokyo has an edge, but it’s unclear whether that will actually translate into the voting behavior of IOC members,” Harada said.

He said there is no indication the oddsmakers’ favorite will be chosen, citing the example of Chicago. The Windy City was tipped as the winner heading into the vote for hosting the 2016 Summer Games, but in the end, Rio de Janeiro won out.

“Odds-on favorite Chicago lost in the first round of voting with only 18 (out of 94) votes. This time Tokyo is favored by bookmakers, but it’s just a prediction,” Harada said

Some of the experts contacted for this story voiced concern that Tokyo’s bid is being dragged down by the radioactive water issue.

Tokyo Metropolitan University professor Naofumi Masumoto, whose studies include the Olympic Games, is one.

“Tokyo’s bid committee officials insist they are working on bringing the games to Tokyo with an ‘All Japan’ commitment. I think they also need to tackle the radioactive water issue with the same ‘All Japan’ effort so the nation can show it’s serious about protecting the environment,” Masumoto said.

If these efforts are not seen as sufficient, he warned, IOC officials might think the Japanese are insensitive to “Olympism,” the term coined to encompass the Olympic movement, which features “the environment” along with the two pillars of sports and culture.

Harada agreed that the government will need to do a good job of explaining what it will do on this matter.

“It’s important for the government to present a work schedule and to show that necessary steps will be taken,” he said.

The government and bid officials are taking a stab at resolving those concerns.

The government announced Tuesday it will dedicate at least ¥47 billion for measures to stop the toxic water problem at Fukushima No. 1. Of that money, ¥32 billion will be used to create a wall of frozen earth around the plant to keep Pacific-bound groundwater from nearby mountains from combining with highly radioactive cooling water accumulating daily in the basements of the buildings housing the crippled reactors, while ¥15 billion will go toward developing more powerful filtering equipment to remove radioactive materials from the contaminated water.

It is believed some 300 tons of radioactive groundwater is flowing toward the sea daily.

Yasushi Aoyama, a professor of public policy at Meiji University, said the final speeches to IOC members will hold the key in landing the Olympics and Paralympics.

Aoyama said conveying how the city can be improved by hosting the games can win votes.

“What I think is necessary is for the Tokyo delegates to show a new model for a city in the 21st century,” Aoyama said, pointing out the dramatic infrastructure and transportation development that took place in Tokyo thanks to the 1964 Olympics, including expressways in the city and the Tokaido Shinkansen Line linking Tokyo and Osaka.

“I think Tokyo could transform into a city that further nurtures its culture and promotes sports,” he said.

Sports journalist Ninomiya stressed the importance of Tokyo drawing up a guideline for “mature” cities, different from the growth model it had for the 1964 Games.

“Tokyo has many tasks to address, including how to deal with its aging population,” he said. “Tokyo can possibly provide the world with solutions. We need to highlight what sports can bring us. I think people can stay healthy by enjoying sports, which could contribute to a reduction in health care costs.”

Meanwhile, Masumoto of Tokyo Metropolitan University said it’s important to play up how Tokyo can contribute to the promotion of the Olympic Movement and its goal of contributing to a more peaceful and better world through sports.

“We can use the legacy of the 1964 Olympics,” he said. “For example, we can hold an event next year commemorating the 50th anniversary, inviting IOC members. Also we can show that sports have taken hold among citizens thanks to the effect of the last Tokyo Games, including volleyball played by mothers.”

Waseda’s Harada believes the outcome depends on the ability of Tokyo’s bid officials to move IOC members with their speeches.

“It’s widely believed that London won the 2012 bid thanks to the inspirational speech by Sebastian Coe, chairman of the bid committee. At the final stage, what matters is not rationality, but emotion,” Harada said.

The winner will be announced at 5 p.m. Saturday local time in Buenos Aires, or 5 a.m. Sunday in Japan.

Tokyo is bidding for the second straight time after losing out on hosting the 2016 Games. It is the third consecutive bid for Madrid, while Istanbul is bidding for a fifth time.