U.S. Presidents have broadened their powers through going public via mass media and through direct presidential action, such as issuing executive orders and executive agreements, as well as expanding the federal bureaucracy and asserting executive privilege.
Presidents have expanded their powers beyond what was initially possessed in the 1800s and early 1900s by developing popular support and other means. The first major way, as mentioned, is by going public, where presidents use various forms of media to appeal directly to the citizens, gaining popular support for their agendas. The advent and evolution of mass media, including radio, television, and social media, have provided opportunities and challenges in shaping public opinion.
The second major way in which presidential powers have expanded is through direct presidential action. This includes the issuance of executive orders and the ability to make executive agreements with foreign nations. Executive orders do not require congressional approval and therefore provide a means for presidents to enforce policy unilaterally, though they lack the permanence of laws passed by Congress. Executive agreements also allow presidents to act in foreign affairs without going through the lengthy treaty ratification process required by the Senate.
Another expansion of power is through the growth and development of federal agencies, like the Secret Service and the Federal Bureau of Investigation, which fall under the executive branch's purview. Additionally, presidents have further developed the concept of executive privilege, which is the right to withhold information from other branches of government or the public. These aspects underscore the complexity and dynamic nature of the presidential powers in the modern era.