U.S. President Donald Trump’s positive coronavirus test has raised the possibility, however remote, that he could become incapacitated or potentially die in office if his symptoms worsen.

While that outcome remains highly unlikely, and few in Washington were willing to discuss it Friday, when Trump was taken to Walter Reed National Military Medical Center for treatment, the Constitution and Congress long ago put in place a plan of succession to ensure that the nation is protected from adversaries and internal conflict when the elected president cannot serve.

The Constitution makes clear that the vice president is first in line to succeed the president should he or she die in office, and can step in to temporarily take on the duties of the presidency should the commander in chief become incapacitated. Vice President Mike Pence, 61, tested negative for the coronavirus Friday.