Final answer:
The ultimate check over all branches of the government is The Constitution.
Step-by-step explanation:
The ultimate check over all branches of the government is The Constitution. It is the supreme law of the land and provides the framework for the powers and limits of each branch of government.
The Constitution establishes a system of checks and balances to ensure no one branch becomes too powerful. While the President, the Supreme Court, and the People all have checks and balances over each other, the ultimate check lies with the Constitution itself.