Is something robotic in the state of Denmark?

COPENHAGEN (Reuters) - The quest for the 2016 Olympics has felt like a rapidly escalating celebrity arms race and come Friday's vote it could all culminate in a robot trying to upstage a president as real and sporting royalty look on.

A prime minister or president has become a must-have accessory for any serious bid after the instrumental role Tony Blair played in bringing the 2012 Olympics to London but the four candidate cities will not rely on statesmanship alone.

While they wait for the president, Chicago have been basking in the support of First Lady Michelle Obama and Oprah Winfrey, frequently cited as the most powerful woman in entertainment.

Madrid have actual royalty on their side in the towering figure of King Juan Carlos, while Rio de Janeiro can boast the sporting variety in the form of 'O Rei' himself, the footballing great Pele.

Tokyo have seemed a little light on star quality but that could all change at their presentation on Friday after bid officials said that POSY, the humanoid robot, could potentially be part of their plans.

So far that is little more than a rumor, but Tokyo, Rio and Madrid could certainly do with something spectacular if they are to ward off the Obama effect Chicago are hoping for.

Chicago hijacked the news agenda with Monday's announcement that President Barack Obama would make a flying visit to address the International Olympic Committee.

Michelle Obama's arrival kept the story going and with her "chit-chat buddy" Oprah alongside her they remained in the spotlight.

"This is a woman who's got a pretty busy schedule -- taping shows, traveling across the globe, a woman with a full plate," the First Lady told reporters on Wednesday.

"Oprah is Oprah. What more do you have to say? I said every single city who's bidding wishes they had Oprah on their team, and we have her."

Chicago's bid is also backed by a group of athletes including Michael Johnson, the multiple Olympic gold medalist.

CYCLING CHAMPION

Madrid had five-times Tour de France winner Miguel Indurain back on a bike in Copenhagen on Thursday, before a news conference hosted by Prime Minister Jose Luis Zapatero.

Tokyo expect Japan's newly elected prime minister Yukio Hatoyama on the eve of the vote.

They have also enjoyed the support of Kanpei Hazama, the comedian and ultra-marathon runner. A sense of humor is clearly important when you are running for hours on end.

Rio have president Luiz Inacio Lula da Silva in town and their bid also has the support of Pele, for many the world's greatest footballer, Gustavo Kuerten, the three-times French Open tennis champion, and Paulo Coelho, the best-selling author.

Coelho's most famous book is "The Alchemist" and what city bidding for the Olympics would not want a man who can turn common metal into gold?

(Additional reporting by Karolos Grohmann)

(Editing by Ed Osmond)