But, save from being limited to a wheelchair, Abbott is a fully-functioning person. He has travelled statewide campaigning for public office. He does not have brain damage or any other infirmity. He has already been on a state Supreme Court and being on SCOTUS is not a physically taxing job. Heck, we have had octogenarians on the bench in all sorts of levels of health. If the Court hasn't been modified for wheelchair access then they are in violation of their own federal law (ADA).
You are right that the Dems are champions of the double-standard but I would think they wouldn't want to touch his disability as an issue. Unlike FDR and JFK where the press hid serious health issues, they can't hide this - not without the elephant in the room becoming obvious. The media would not ignore it - especially if Bush trots him out for the big introduction the way he did for John Roberts. So if the Dems go into their typical baseless hysteria, it will be seen to many as if they are attacking a man in a wheelchair.
Some of the Dem-friendly media may try to keep that appearance away using tricky camera angles but it will be difficult to hide, especially if Bush introduces him as the first handicapped American nominated for the Supreme Court.