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When the delegates of the states gathered in Philadelphia in the summer of 1787 and wrote the Constitution, they distributed the powers of the federal government among two Houses of Congress, a President, and a judiciary, and required in many cases that two of them work together to exercise a particular constitutional power. That separation of powers protects the liberties of the American people by preventing any one officer of the government from aggregating too much power.
The Framers of the Constitution did not give the President the kingly power to appoint the senior officers of the government by himself. Instead, they allowed the President to name an individual for a senior office, but then required the President to obtain the Senate’s consent before appointing the individual to office. Thus, they required the cooperation of the President and the Senate to put someone in high office.
Many of the Framers had practical experience with government and recognized that not every office would be of sufficient authority and consequence as to merit the attention of both the President and the Senate to an appointment to the office. Therefore, they provided a means by which the Congress by law could decide which of the lesser offices of government could be filled by the President alone, a court, or a department head.
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via Speed Up Presidential Appointments, But Do Not Enact S. 679 | The Heritage Foundation.