Mr George Bush's campaign team have played down reports that the US president was fitted with a transmitter to allow him to receive help during a televised debate with rival Mr John Kerry.
During the public discussion with Mr Kerry, an apparent bulge could be seen in the middle of Mr Bush's back under his suit jacket.
A number of websites have claimed that the president was wearing a device that allowed an adviser to feed him answers to questions during the debate last week.
It was also alleged that on several occasions Mr Bush stopped speaking for a period and stared ahead as if listening to a voice. Other reports suggested the president could have been wearing a bullet-proof vest.
The White House refused to provide an on-the-record comment, saying that it would not dignify a baseless issue, and referred questions to the Bush-Cheney campaign.
Mr Bush's campaign spokesman told the Washington Postthe claims were "preposterous", but declined to elaborate or to suggest what could have produced the unusual photo.
The president's tailor, who made the suit, said the bulge was nothing more than a fold along the jacket's back seam, accentuated when the president crossed his arms and leaned forward on the lectern.
Mr Dave Lindorff, a reporter with the news and current affairs website Salon.com, was one of the first to suggest the apparent bulge could be a device.
He said the device would not necessarily have been electronic, as there are magnetic and fibre-optic technologies that can achieve the same effect.