At Thursday's Republican debate, Marco Rubio suggested that the Second Amendment is second because the founders saw it as the second most important right in the Bill of Rights. "It's the constitutional right of every American to protect themselves and their families," Rubio said. "It is the Second Amendment for a reason."
This is wrong. The amendments are actually in the order they're in to align with the articles of the Constitution.
Brian Palmer explained for Slate:
The original first amendment, which did not pass, outlined how the number of seats in Congress would rise in response to population growth—a modification of Article I, Section 2 of the Constitution. The original second amendment, which initially fell short of ratification and later became the 27th Amendment, banned members of Congress from raising their own salaries before voters had an opportunity to oust them. That related to Article I, Section 6, which deals with congressional compensation.
The now-sacred First Amendment was originally slated to sit in the far less distinguished third position. That doesn't mean the founding fathers thought congressional salary more important than the freedom of speech. Rather, the First Amendment relates to the powers of the legislature, which come later in the Constitution than does the structure of Congress. According to Yale professor Akhil Reed Amar, the provision we now know as the First Amendment begins with the phrase "Congress shall make no law" because it contrasts with Article I, Section 8, which begins "Congress shall have power."
The Second, Third, and Fourth Amendments limit what Congress may do, extending the list of proscriptions found in Constitution's next provision, Article I, Section 9. Amendments five through eight, dealing with such issues as juries, bail, and cruel and unusual punishment, limit the government's judicial powers. They relate to Article 3 of the Constitution, which establishes the court system. The final two amendments from the Bill of Rights are guides to interpreting the Constitution as a whole, and likely would have been added to the end.
So there you have it. The Second Amendment's placement has nothing to do with the founders' views of its importance.