When the U.S. decided to bid for the 2024 Olympics, many experts felt an American city would be an early front-runner in the global race. Now, it's uncertain whether the bid will even make it to a final vote.

International Olympic Committee members are watching with a mixture of surprise and puzzlement as Boston, reeling from a lack of public support, struggles to keep its bid afloat.

For the moment, the future of the bid hinges on a statewide referendum in November 2016 — a move that leaves the candidacy in limbo until then and raises the possibility of the city dropping out midway through the campaign.

"It's a calculated risk," longtime IOC member Dick Pound of Canada told The Associated Press. "It means you're going ahead, making all these plans and carrying all these expenses without knowing whether somebody's going to suddenly pull the plug on you."

Speculation is the plug could be pulled sooner, although the U.S. Olympic Committee denied a report in Wednesday's Wall Street Journal that it may drop the bid if local support does not improve soon.

"We believe that Boston can and should lead America's bid to host the 2024 Olympic and Paralympic Games, and we are absolutely committed to our partnership with Boston 2024 and their innovative concept for hosting the games," USOC CEO Scott Blackmun said. "Any suggestion that we are considering alternatives is simply not true."

The latest poll by Boston's WBUR radio station found that only 36 percent of the city's residents supported the bid — a figure that dropped from 51 percent in January. Many residents fear the Olympics will generate cost overruns and leave tax payers to foot the bill.

"The USOC made a decision and we are moving forward with that," Anita DeFrantz, a USOC board member who also sits on the executive board of the International Olympic Committee, told the AP. "There's going to be a referendum. That's OK. The people are taking their time to learn the facts."

It's been a bumpy road for Boston ever since the USOC surprisingly picked the Massachusetts capital in January over rival bids from Los Angeles, San Francisco and Washington.

Low polling results, political controversy and public relations missteps have beset Boston, which was seen by the USOC as the city with the best chance of bringing the Summer Olympics back to the country for the first time since Atlanta hosted the 1996 Games.

The stumbling start has raised questions: Should Boston have been picked in the first place? Did the USOC not realize the depth of local opposition? Can public opinion be turned around for a referendum to pass? Could another U.S. city replace Boston?

After initially resisting calls for a referendum, Boston bid leader John Fish said last week the privately-funded body would help gather signatures to put a vote on the state ballot in 2016. Even if the measure passes statewide, he said, the bid would be scrapped if it is rejected within the city of Boston.

"The USOC probably had some indication of the level of support of the population in different candidate cities they had nationally and I'm surprised they did not take this more into consideration," Swiss IOC member Denis Oswald said.

After stinging defeats for New York and Chicago in bidding for the 2012 and 2016 Olympics, the timing had seemed right for the U.S. this time. The USOC had settled a festering dispute with the IOC over revenue-sharing. USOC chairman Larry Probst and Blackmun made inroads in repairing relations with the international Olympic world. IOC President Thomas Bach and other members encouraged the U.S. to come forward.

Boston, Rome and Hamburg, Germany, are the declared 2024 candidates so far. Paris is expected to join the race soon. Other potential contenders include Istanbul, Turkey; Budapest, Hungary; Baku, Azerbaijan; and Doha, Qatar. The IOC will choose the host city in 2017 in Lima, Peru.

Hamburg plans a referendum on its bid later this year. Paris and Rome have not indicated plans for public votes.

Some IOC members wonder whether the USOC would replace Boston if it dropped out. But the timing of the referendum would make that impossible.

The IOC executive board will meet in April or May of 2016 — six or seven months before the Massachusetts vote — to select a short list of finalists. The IOC won't reopen the race to let in another city.

The scenario has parallels with the troubled race for the 2022 Winter Olympics, with multiple cities dropping out. Oslo, once seen as a natural favorite, suffered from paltry public support and eventually pulled out when the Norwegian government refused to back the bid.

"I don't know why they are waiting so long," Oswald said of Boston's referendum plans. "The uncertainty which will last until they have a final decision, whether or not they have the final support at the end, is not good for the candidature."

The possibility of Boston going out earlier is another matter. Technically, there would be time for the USOC to replace Boston, as the deadline for submission of bid cities to the IOC is Sept. 15.

The most likely alternative would seem to be Los Angeles, which hosted the Olympics in 1932 and 1984.

"But I don't know where LA would be parked on this either," Pound said. "To say Boston is withdrawing in favor of LA, they might say, 'Hey, wait a minute.'"

Senior Norwegian IOC member Gerhard Heiberg, who witnessed firsthand the demise of the Oslo bid, said Boston's poll results are "not a good sign" but a referendum may be the right move.

"They have to go out and lobby for this," he said. "They have to organize meetings with business, local authorities and the public. They have to go out and show why they think this is right."

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