The statement that the Vice President serves as President of the Senate and succeeds the President upon vacancy is a matter of constitutional definition and everyday civic knowledge, requiring no formal citation.
The claim outlines foundational constitutional roles (Article I, Section 3, Clause 4 and the 25th Amendment of the U.S. Constitution) that are universally accepted facts of U.S. government structure. None of the retrieved papers specifically evaluate or test this dual constitutional fact as a contested research question, rendering it common knowledge.