I understand the point the article is trying to make, I believe though I disagree. Granted I was quite young under Carter, but seems to me that most folks just felt kinda sorry he was obviously so over his head. He was a terrible president, but I just don't remember anyone questioning he meant well for the US.
Nixon? There were serious questions about him and his agenda. There were those that thought he was great and those that despised him. Seems to me to be a better analogy with Obama.
As for rankings, yeah that's where Carter and Obama may marry up.
Carter was way over his head, but he dd a better job then obama could ever dream of doing