Final answer:
The most radical departure from previous political documents in the Declaration of Independence is the argument that citizens have the right to overthrow an unjust government.
Step-by-step explanation:
The most radical departure from previous political documents in the Declaration of Independence is the argument that citizens have the right to overthrow an unjust government. In the Declaration, Thomas Jefferson wrote that whenever a government becomes destructive of the people's rights, it is the right of the people to alter or abolish it and to establish a new government. This idea of overthrowing an unjust government was not common in previous political documents and marked a significant shift in political thought.