Why is it not a question when the sentence starts with "be"? I don't understand the structure of this sentence.
I can understand how this may be confusing! This sentence doesn't actually start with "be." It actually is a fragment of an entire sentence. The beginning of the sentence actually is "Millions of citizens involved in the 2020 presidential campaign..." You actually can use "be" at the beginning of a sentence. It does not have to be for questions. Verbs can be used at the beginning of the sentence when it is a command. Ex: A: I don't want to go to school. I hate school. B: Be that as it may, you still need to go to school. Ex: Be a dear and grab that cup for me. Ex: Be the best student you can be.