At any moment if the president is impeached or dies the Vice President will be the next in line.
The main purpose of both documents is to assert the rights and freedoms of the people to form their own governments -- governments which will protect their rights as citizens.
Historical context:
The Declaration of Independence (1776) asserted the American colonies' decision to break away from British government. It included the same Enlightenment ideals of natural rights and liberties that would characterize the Declaration of the Rights of Man and Citizen produced later (1789) in France.
The Declaration of the Rights of Man and the Citizen is a fundamental document of the French Revolution, which was written by Abbé Sieyès and the Marquis de Lafayette. Abbé Sieyès was a prominent clergyman in France who supported the rights of the common people. The Marquis de Lafayette was a member of the nobility who had fought in America's war for independence against Britain. Their document was written in consultation with Thomas Jefferson of the United States, who had drafted the Declaration of Independence.
