Explanation

The primary bulwark against tyranny and executive overreach in constitutional governance is the Separation of Powers:

– Formulated by Montesquieu, dividing state functions across three autonomous organs (the Legislature, the Executive, and the Judiciary) establishes an effective system of checks and balances.
– When powers are demarcated, no single branch can exercise unchecked authority or arbitrarily infringe upon civil liberties without institutional restraint.
– A ‘committed judiciary’ historically connotes a judiciary subservient to the prevailing executive ideology, which endangers liberty rather than protecting it.
– Similarly, centralization of powers leads toward authoritarian control, and mere electoral majoritarianism can result in majoritarian overreach.

Hence, the best safeguard of liberty is the Separation of powers — Option D.