RONALD REAGAN'S son has claimed that the late president suffered the early stages of Alzheimer's disease while still in office, the first time such an admission has been made by a relation or associate.
It has provoked a war of words between Ron Reagan (52), a liberal broadcaster, and his elder half-brother Michael. Both are publishing books to coincide with the 100th anniversary of Reagan's birth next month.
Critics have previously claimed that Reagan was not fully in touch in the latter stages of his presidency. Some doctors have blamed Alzheimer's, which severely affected the president in his final years before his death in 2004 at the age of 93, although it was not officially diagnosed until 1994, five years after he left office.
In his book, Ron Reagan said he first grew concerned about his father's behaviour in the mid-1980s. "There was just something that was off. I couldn't quite put my finger on it," Mr Reagan told ABC.
He suggested that he saw hints of confusion and "an out-of-touch president" during the 1984 campaign debates with Walter Mondale.
After 1986, he observed that the president was using note cards as he spoke on the telephone in the Oval Office. It was around that time that Mr Reagan referred to Princess Diana as "Princess David" at a White House function.
Mr Reagan believes that had his father received a diagnosis of Alzheimer's in 1987, he would have stepped down, but argued that the illness was not severe in office and should not mar his legacy. "This no more discredits or defines his presidency than Lincoln's chronic depression, Roosevelt's polio, Kennedy's Addison Disease... any of those things," he said.
Michael Reagan, a conservative political consultant, denied that his father had suffered Alzheimer's in the 1980s and accused Ron of wanting to "sell out his father to sell books". (© Daily Telegraph, London)