Party Over Branch
In a sense, when an officeholder takes the oath of office, they are pledging to serve the role of their branch of government.
Historically, this idea is more wishful thinking than reality, dating back to the nation’s founding. During George Washington’s administration, Secretary of State Thomas Jefferson was a vigorous rival of Alexander Hamilton, the Treasury Secretary. Hamilton’s advocacy for a strong central federal government—through financial and other policies—was opposed by Jefferson and others, resulting in a split between two emerging political factions: the Federalists, represented by Hamilton and Washington’s policies, and the Republicans, led by Jefferson, James Madison, James Monroe, and others who favored a decentralized government and a stronger legislative branch.
Jefferson was notorious for serving in the Executive Branch while quietly undermining Washington and his bitter rival Hamilton by conspiring with political allies in the Legislative Branch. He considered Washington’s Proclamation of Neutrality an overreach into Congress’s authority to declare war and, implicitly, to determine neutrality. Instead of defending the Executive Branch’s prerogative, Jefferson worked behind the scenes with his congressional allies to attack Washington’s policy and weaken the very branch of government in which he served.