PARIS (AFP) - Chicago, Madrid, Rio de Janeiro and Tokyo, all vying to host the 2016 Olympics, get their chance over the next month to impress the International Olympic Committee (IOC) with the physical reality of their bids. Prior to the arrival of the IOC Evaluation Commission, led by Morocco's former 400 metres hurdles gold medallist Nawal El Moutawakel, all four have only been able to make presentations as they try and convince IOC members to vote for them in Copenhagen on October 2. However, now the quartet have the opportunity to show a modest smattering of IOC members the practicality of their respective bids. Chicago will get the first bite this week. Once considered the frontrunners, according to the influential GamesBid.com site, they have slipped to fourth after a series of apparent setbacks. But their bid leader Pat Ryan is adamant that he and his team are not nervous. "I'm very engaged and excited about showing them the city," the silver-haired owner of the Chicago Bears told AFP. "We will make the city come alive for them. It is hard to envision it unless you see it for yourself. "When you see 200 metres away from a venue there is a famous museum and then you look across the street and see good restaurants, then it is quite easy to envision. "One out of town visitor who I showed the sites to the other day simply replied 'this city was built for the Olympics'." However, while the Windy City's star may have dimmed, the support of President Barack Obama, a former Illinois senator, is still a powerful weapon. Chicago's rivals fear the impact he could have on the result. They are only too aware of the influence exerted by former British Prime Minister Tony Blair and Russian President Vladimir Putin when they lobbied in the lead-in to the vote on the respective bids of London for 2012 and Sochi for 2014.One such person to voice such an opinion is former IOC President Juan Antonio Samaranch."There are four candidates and each one has its programme and possibilities. Obviously the presence of Barack Obama could be a positive point for Chicago's candidacy," he told AFP in February. However, Samaranch still wields influence and will be a significant factor for Madrid's candidacy, his son Juan Antonio junior, an IOC member, is one of the leaders of the bid, while the glamorous Mercedes Coghen has been seen to be the bid leader with the most natural charm. Coghen, herself an Olympic gold medalist with the field hockey team in 1992 in Barcelona, is stressing that Madrid would be a 'green' Games. "We want Madrid to be seen as the Green Games model," she said."A city where the energy will be renewable, the materials recyclable, and the transport completely public."Madrid's main concerns are over racist incidents which have plagued football matches in the country and has been one of the major worries for the IOC.Tokyo have also described their Games as environmentally-friendly and that it will be extremely compact. They say it will open up further the huge potential of the Asian market, though, many believe it would be too soon to take the Games back to the region after Beijing's successful hosting last year. Tokyo can boast sound financial backing and solid government support - even if former Olympic shooter and now Prime Minister Taro Aso has all-time low poll ratings - as well as enormous popular support. Bid chief Dr Ichiro Kono insisted Tokyo would be an athlete-friendly Games in line with the way they hosted the 1964 Olympics. "Tokyo 2016 is deeply committed to creating an ultra-compact, barrier-free Olympic and Paralympic Games in the heart of what is already one of the world's most accessible cities," said Kono. Rio de Janeiro have fought back strongly from being the rank outsider of the quartet when the shortlist was announced last year. The popularity of bid leader Carlos Nuzman has boosted their chances of bringing the Games to South America for the first time. Set against that is that some IOC members are not happy to give it to them just after Brazil has hosted the 2014 World Cup finals. "We do not want to be the dessert after the main course," said one observer.