Final answer:
A major source of power for a president in a presidential system is the use of executive orders, which allows the President to issue directives with the force of law without Congressional approval.
Step-by-step explanation:
The best explanation for a major source of power for a president in a presidential system is executive orders. While judicial appointments and the ratification of treaties are significant presidential powers, they require the advice and consent of the Senate. An executive order, however, is a directive from the President that has the force of law and does not require Congressional approval, making it a potent tool at a President's disposal. For instance, a presidential executive order can enact policy changes or clarify the implementation of existing laws without needing to pass through the legislative process.
Examining the checks and balances within the United States government, the legislative branch maintains power over the courts predominantly through three means: requiring Senate approval for the appointment of justices and federal judges, the ability to rewrite laws that the courts have declared unconstitutional, and the power to withhold funding to execute court decisions (Option d from question 23). These checks help to ensure a balance of power between the branches of the government.
Understanding the legislative-executive branch relations is key. In a presidential system, there is a separation of powers which allows for independent decision-making between the legislative and executive branches, which is fundamental to the operation of the system.