Actually, I'm not sure it was the press. Roosevelt himself didn't want to project an image of weakness, and he thought that some folks might take his physical disability that way. He wore heavy leg-braces, and when he walked, he used a cane (rather dapper in some circles) and had someone right beside him whose arm he could lean on for support.
His personal appearances were carefully "choreographed" to show as little of him having to walk as possible. Especially such things as getting out of or into an automobile or limo. This is one of the very few published pictures showing FDR in a wheelchair (note the leg-brace on the little girl's right leg). HERE.
Everybody knew about it, of course. But the message he managed to project was "It's a matter of no importance."
Roosevelt never accepted the idea that his paralysis was permanent, and spent whatever spare time he could find at a spa in Warm Springs, Georgia, undergoing hydrotherapy and physical therapy. He wound up buying the place (on his own dime, by the way; the Roosevelt family was independently wealthy—"old money") and turned it into a rehabilitation center for polio victims. This was in 1927, incidentally, before he was elected President. He also started the "March of Dimes," which went a great way toward funding research for a polio vaccine.
As I said, his disability didn't slow him down one bit, and to try to use it for propaganda points against him might just backlash on whoever tried it.
Adage: There is an essential difference between a career politician and someone who dedicates his life to public service.