Final answer:
The error in capitalization is in option a, where 'Democracy' should not be capitalized, it should be 'democracy'.
Step-by-step explanation:
The sentence that contains an error in capitalization is:
a. "The Electoral College goes against the very principles of Democracy that the United States was founded upon; it discounts millions of ballots while simultaneously prioritizing various citizen’s votes based on their geographical locations, which essentially gives land more power than people."
The error is in the word 'Democracy'. In the context provided, it should not be capitalized as it is not a proper noun or at the beginning of a sentence. Therefore, the correct sentence should be: "...the very principles of democracy..."