The word “demographic” refers to a specific group of people’s characteristics, traits and other defining information within the group.  For example: The students currently attending “Small Town USA” High School.  A survey (questionnaire) administered among the student body might ask their place of birth, how many siblings they have, what is their grade point average, what sort of career are they interested in, do they participate in any of the school’s extracurricular activities, and so on.
After the completed student surveys have been turned in, the results are compiled and can be demographically evaluated.  The survey reveals the majority of students were born in Small Town USA, they have two siblings, their GPA is 3.0, the majority of the kids are undecided about their career choice, and high school sports is the predominant after-school-activity-of-choice.
The school is holding an election for student body president two months from now, and Susan Garcia has decided to enter the race.  Susan has decided to run her campaign as the candidate who would be a demographically symbolic school president because she was born in Small Town USA, has two brothers, carries a 3.0 GPA, is undecided about her future career and she is a stand-out player on the girls varsity softball team.  Susan’s foregoing details would allow her to run for election as the candidate who would be the “demographically symbolic president” of Small Town USA High School.  The significance of this fact for Susan is: She is the candidate who most closely aligns with the majority of the student body; the other kids can relate to her.
Applying this same logic to the American Presidency,  the overwhelming majority of presidents were not demographically symbolic.  I will close-out this answer right here.  The next question I would ask along these lines is: “What were the most common reasons that led the American populace to vote for a man who did not demographically represent them?”