Truman survived. He was also in the 30’s later into his first term than Obama. He started picking up in early ‘48 and managed to climb up back high enough in time for the election.
Obama’s closest match is hey hey hey, LBJ, who hit 39 and then started to climb again. Carter was much lower than Obama is now.
Carter had more legitimate polling, and less of it.
There's no way, IMHO, that Obama is more popular than Carter was.