How has the president's power as the chief executive grown?

The powers of the President have grown much over the years. The Constitution originally gave the president powers in several areas. It appointed him Commander in Chief of the military. The founders wanted a civilian military leader, so as to check the power of the military. The Constitution also gave the President several diplomatic powers: the power to make treaties (with the advice and consent of the Senate), ceremonial duties of representing the United States at home and abroad, and the power of recognizing new and existing countries by receiving their ambassadors. The President was given wide powers to appoint various positions in the government. S/he can appoint: "ambassadors, other public ministers and consuls, Judges of the Supreme Court, and all other Officers of the United States." (Constitution, Article II, Section 2).

Over the years, via practical exercise of powers not specifically given to him, the powers of the president have grown. Expansion of presidential powers began early on, with George Washington, who invented the idea of "executive privilege" when he refused to turn over notes about treaty negotiations for a controversial treaty. Washington also began the tradition of Executive Orders, which are orders issued by the President that have the force of law without having to be approved by Congress. All following presidents have engaged in issuing Executive Orders, some more than others. 

Indeed, many of the abuses/expansion of presidential power began in the early days of the republic. Andrew Jackson liked to engage in a bit of nepotism by appointing his friends and people who were loyal to him to various governmental posts. Abraham Lincoln greatly expanded presidential powers during the Civil War by assuming emergency powers. The largest expansion of presidential power by Lincoln was the suspension of habeus corpus, which is the right to appear in court for a trial when accused of a crime. 

However, the main example of the expansion of presidential powers is the ability to make war. While the Constitution allocates the power to declare and fund war to Congress, the President has often sent troops into battle without first consulting with Congress. Lincoln ordered the military to blockade Southern ports while Congress was not in session in response to an attack by the South, effectively engaging in warfare without Congressional approval. Lincoln knew he had overstepped his constitutional powers, and he asked Congress to retroactively approve by declaring war when they returned, and they did so. Teddy Roosevelt took military action in Panama and the Dominican Republic sans Congressional approval. Harry Truman sent troops to Korea to what would eventually be known as the Korean War without prior authorization from Congress. Kennedy used the CIA and the military to execute the ill-fated Bay of Pigs operation in Cuba, without authorization. Johnson and Nixon engaged in the Vietnam War without a formal declaration of war from Congress. Many presidents have flouted the war powers of Congress.

Congress obviously did not like these actions, and in 1973, it passed the War Powers Resolution, a law intended to limit the power of the President to deploy troops without a formal declaration of war. However, while it did provide some limits on presidential warmaking powers, such as a limit to the length of time the military can be deployed and a veto for Congress that allows the legislative branch to force the President to immediately recall deployed military, it codified the right of the President to engage in military action in law. The War Powers Resolution stipulated that the President can send troops without notifying Congress, but he must notify Congress within 48 hours of the military deployment. This in effect gave the President permission to deploy the military without first consulting with Congress. 

George H. Bush engaged in the first Gulf War because Iraq invaded Kuwait, taking advantage of the ability to send troops without prior approval. Congress granted an unprecedented amount of warmaking power to George W. Bush in 2002, when Bush got Congress to approve a resolution giving him the power to declare war, when he wanted to, without prior consultation with Congress. As a result, Bush declared war on Iraq in 2003. 

War has often been used as an excuse to exceed the powers given to the President in the Constitution, even from the earliest days of the United States. In 1798, John Adams had Congress pass the Alien and Sedition Acts, which granted the executive the power to jail political dissenters and deport any noncitizens he deemed to be a threat to the U.S. Franklin Delano Roosevelt demonstrated one of the most egregious unjust expansions of presidential power when he insisted that U.S. citizens of Japanese descent be put into internment camps, in order to protect the country during World War II. 

War has not been the only expansion of powers, however. FDR created many new agencies under the New Deal, all of which fell under the control of the Executive Branch. FDR also tried to expand the number of justices on the Supreme Court in order to pack the court with judges more favorable to his initiatives (he failed). Harry Truman seized steel mills in the U.S. because of a steel workers' strike, an unprecedented move. Richard Nixon was eventually caught engaging in illegal activity with the Watergate scandal. Nixon and his operatives engaged in spying on political opponents via electronic surveillance, and they used the FBI, CIA, and the IRS to harass political figures who opposed Nixon and activist groups. Nixon tried to use executive privilege to avoid releasing incriminating audio tapes, but was unsuccessful. 

Thus, presidential powers have expanded in many areas since the founding of the United States. These are a few examples of the main areas of expansion.