Soon, America will celebrate the 100th birthday of that actor who was president during the 1980s, Ronald Reagan. How will sons Ron Jr. and Michael honor their father? By bickering on television about whether he had Alzheimer's in office.

Ron Reagan Jr., the liberal son, has a new book titled My Father at 100 where he reflects on his father's life. His publicity appearances so far have focused on one aspect of his book: That he thinks his dad "exhibited signs of Alzheimer's" disease for the majority of his presidency. Happy 100th birthday!

In his new book, "My Father at 100" (Viking), Ron Reagan - the youngest son of former President Ronald Reagan - claims his father exhibited signs of Alzheimer's three years into his first term.

Doctors diagnosed Mr. Reagan with the memory-robbing disease five years after he left office, notes CBS News senior White House correspondent Bill Plante.

"Knowing what we know now, about the nature of Alzheimer's disease, we know that, decades before symptoms begin arriving, changes are happening in the brain," Ron Reagan writes.

He said he was alarmed by his father's performance in his Oct. 7, 1984 presidential debate with Democratic challenger Walter Mondale. He writes of that day, "My heart sank as he floundered his way through his responses, fumbling with his notes, uncharacteristically lost for words. He looked tired and bewildered."

Would his ultra-conservative brother, talk radio host Michael Reagan, agree with this retrospective diagnosis? This sounds like a "no:"

Michael Reagan went on CBS' Early Show today — clip at the top — to say more. (He too is promoting a new book about his father.)

On CBS' "The Early Show" this morning, Reagan, a political consultant for the Reagan Group, said, "All these years I've listened to people like Bill Maher and other people on the left who inferred my father had Alzheimer's when he was President of the United States to somehow discount the great job my father did as president.

"So now for one of his sons to come out and in fact say, 'Yeah, he might have had Alzheimer's or he had Alzheimer's during that time,' just gives credence to people like Bill Maher and others. It absolutely offends me that somebody would say that when there's no evidence anywhere on the planet to back it up," he told anchor Erica Hill.

Everyone loves a good Reagan Fight.