The secret ballot vote will be taken on Wednesday.
SINGAPORE (AP) -- British Prime Minister Tony Blair came to lobby for London.
Spain's Queen Sofia flew in to make the case for Madrid.
New York Mayor Michael Bloomberg arrived to stump for the Big Apple.
Dignitaries from Paris and Moscow campaigned frenetically in the lobbies, hallways and bars.
With three days before the vote on the host city for the 2012 Olympics, the campaigning went into overdrive Sunday -- and the five-ring show will only get more intense in the next two days and final hours of the most prestigious race in Olympic bid history.
By all accounts, Paris remains the city to beat in Wednesday's secret ballot of the International Olympic Committee. London is regarded as the main challenger, with Madrid and New York as upset hopefuls, and Moscow a long shot.
"There is no reason to believe that Paris is still not perceived as the front-runner," senior Australian IOC member Kevan Gosper said. "You have to put London next to them.
"My bottom line is it's still between those two, and I think it's close," Gosper said. "But in this organization, we're great at delivering surprises. You never know."
Blair first to arrive
Blair was the first head of government to arrive for the final push, praising London's "very, very strong bid."
He and his wife, Cherie, are expected to meet with many IOC members before leaving to host the G-8 summit starting Wednesday in Gleneagles, Scotland.
"I'm here, in a way, to say that it's a bid that's got the enthusiastic support of the British people, of all the political parties and the government," Blair said. "The country is right behind it.
"It will be a great games for the athletes. It will leave a legacy not just for sport in the UK but for the Olympic movement as well, and that's important."
French President Jacques Chirac -- who has clashed with Blair over European Union issues and the war in Iraq -- is due to arrive Tuesday to boost the Paris bid.
Chirac will take part in Wednesday's final presentations to the IOC before leaving for Scotland.
Queen Sofia arrived Sunday
Queen Sofia arrived Sunday and will be joined by Spanish Prime Minister Jose Luis Rodriguez Zapatero.
Also due in Singapore are Russian Prime Minister Mikhail Fradkov, U.S. Sen. Hillary Rodham Clinton and a slew of sports stars, including Muhammad Ali, David Beckham and Tony Parker.
The influx of politicians and celebrities has raised questions about how far the boosters can go in selling the bids. While it's OK for Blair or other leaders to take IOC members to dinner, IOC ethics rules prohibit "overt" public promotional events, spokeswoman Giselle Davies said.
"Let's not focus on celebrities, let's concentrate on what this is about, and that's the bid file," she said.
Lobbying in full swing
Lobbying was in full swing Sunday throughout the Raffles Convention Center and adjoining hotels used by IOC members, bid officials and the media. IOC members began trickling in from around the world. About 100 delegates will be voting Wednesday.
British Olympic Association president and IOC member Craig Reedie said as many as 30 members may not yet have decided how they will vote.
Among the undecided members is Australia's Phil Coles, who said Wednesday's final 45-minute presentations to the IOC could be crucial.
"In the past, it was always the feeling that the final presentation was hardly likely to win the bid but you could always lose it on that," Coles said. "Here, I think because of the closeness of it, the presentations might make a lot more difference."
The IOC executive board began meeting Sunday, and is scheduled to consider New York's revised Olympic stadium plans today.
Last month, after New York state officials rejected a proposed $2 billion stadium on Manhattan's West Side, the bid team came up with an alternative stadium plan in Queens for hosting the opening and closing ceremonies, track and field events and soccer.
The new plan has been endorsed by the world governing bodies of soccer and track and field, but still requires formal approval by the IOC board. There have been no indications the proposals won't be accepted.