When a monarch dies, power stays in the family. But what about a president? It was a tricky question that the founders left mostly to Congress to figure out later. Lana Ulrich, of the National Constitution Center, and Linda Monk, constitutional scholar and author of The Bill of Rights: A User's Guide, explain the informal rules that long governed the transition of presidential power, and the 25th Amendment, which outlines what should happen if a sitting president dies, resigns, or becomes unable to carry out their duties.