Geoffrey C. Ward had to cut away from watching a presidential news conference to talk to a reporter about “The Roosevelts: An Intimate History,” the new Ken Burns documentary series he wrote.

That brought Mr. Ward to a favorite theme: his conviction that neither Theodore nor Franklin D. Roosevelt could be elected president today. Teddy Roosevelt, with his shrill voice and penchant for outbursts, was “too hot” for the cool medium of television, he said, while “clearly, Franklin was a cripple,” paralyzed from the waist down after contracting polio in 1921, at 39, and today’s press “would compete to see who could find him most helpless.” Yet both succeeded, in part by skillful manipulation of their images in the news media of their eras, one of many threads the 14-hour series explores....

The documentary, Mr. Ward said, is also the “first systematic treatment on film” of all the efforts Franklin Roosevelt — president from 1933 to his death in 1945 — made to appear to walk. It took him seven years to perfect the move of swinging his body forward while holding onto someone’s arm. The man who used a wheelchair and couldn’t get to the bathroom on his own “made everyone believe he stood up to greet them,” Mr. Ward said. “He was an absolute magician.”

The modern view “is to see a kind of conspiracy on the part of Franklin Roosevelt to hide the fact that he had this disability from the public,” Mr. Woolner said.

But he added that the public was well aware of his polio; there were fund-raisers every year for research into the disease. What the public didn’t know, he said, “was the extent of his disability,” his ability to put people at ease somehow convincing them that he had overcome it.

Political necessity required an image of strength and health while running for election as the country struggled with the Depression....

The gap between image and reality is of particular interest to Mr. Ward, who had polio when he was a child and wears braces. Through his long collaboration with Mr. Burns — he wrote “Jazz,” “Baseball” “The War” and “Prohibition,” and was a writer of “The Civil War” — Mr. Ward has never gone on camera. But in this series, he appears as an expert, and when discussing Franklin in the fourth episode — much of which is devoted to Roosevelt’s polio struggle — he becomes emotional.