The three cities vying to host the 2020 Olympics are making their pitches to IOC members, hoping to seize the momentum in the final two months before the vote.
Istanbul, Madrid and Tokyo were laying out their plans on Wednesday to the general assembly of the International Olympic Committee, the first time they have made presentations directly to the electorate.
Of the IOC's 100 members, 86 were attending the proceedings. Among those absent were FIFA president and Swiss member Sepp Blatter and Britain's Princess Anne.
It's a potentially pivotal moment for the cities in the run-up to the September 7 vote in Buenos Aires, Argentina. It was at a similar meeting in 2009 that Rio de Janeiro won over the members in the race for the 2016 Olympics.
Up first in the presentations was Istanbul, whose bid has been shaken by the anti-government protests that swept Turkey last month. Madrid and Tokyo were to follow.
The meetings were taking place behind closed doors at the Beaulieu convention centre. Each delegation had 45 minutes to make speeches and show videos, with another 45 minutes allotted for questions and answers.
Last week, the IOC released a technical evaluation report on the cities to give members as much factual information as possible. The report did not rank or grade the cities, but Tokyo appeared to come out the best overall.
Istanbul is bidding for a fifth time, Madrid is back for a third consecutive time and Tokyo is trying for a second time in a row.
Istanbul is inviting the IOC to take the Olympics to a new region, to a predominantly Muslim country for the first time, to a city that connects Asia and Europe.
Tokyo claims to be a "safe pair of hands'' at a time of global economic and political uncertainty.
Madrid, despite Spain's severe financial troubles, boasts that it would spend far less money than the others on infrastructure because 80 per cent of its venues are already in place.
Istanbul probably had the most at stake on Wednesday, needing to reassure members in the wake of the unprecedented street demonstrations across Turkey last month that led to a crackdown by the government of Prime Minister Recep Tayypip Erdogan.
"Although the games will be seven years ahead, what's going on (in Turkey) right now is important to the voting of the members,'' senior Norwegian IOC member Gerhard Heiberg said.
"There will be many questions, absolutely. This is a good opportunity for Turkey, for Istanbul, to answer the questions and lay it out in the open how they think, what they're going to do about it.''
On Thursday, the six candidates running to succeed Jacques Rogge as IOC president will present their manifestos to the assembly.
Rogge is stepping down in September after 12 years in office.
The contenders are: IOC vice presidents Thomas Bach of Germany and Ng Ser Miang of Singapore, executive board members Sergei Bubka of Ukraine and C.K. Wu of Taiwan, and former board members Richard Carrion of Puerto Rico and Denis Oswald of Switzerland.