19th century Republican constitutionalism was based on several important principles, which were clearly expressed in public policy. Republicans believed heavily in the legislative independence based on the separation of powers, and a strict construction of congressional power and states' rights. They were also concerned with the relationship between citizens and government, the distribution of power among the different branches of government, and the limits on governmental power in the interest of individual liberty.
The ideas and principles of Republican constitutionalism were expressed in different areas of public policy in several ways. Jefferson changed the presidential office and its role in the government by making it a popular institution instead of a counter measure. To assert a strong executive leadership in congress, he often had his political lieutenants placed in key legislative and political positions, and worked through them to effect his legislative program. He vigorously employed executive power, in particular by relying on skills of persuasion but also occasionally by using the power of legal compulsion and military coercion.
Under the separation-of-powers doctrine the legislative branch could always claim to be in a special sense the voice of the people, but starting with Jefferson, presidents could make the same claim by virtue of their identification with a political party. Jefferson did not, weaken the executive branch by making these changes to it, but rather he worked it into the system. He solved the problem of coordinating the political branches within the separation-of-powers framework through the great prestige and unquestionable ascendancy he possessed as a party leader. He met with congress in caucuses in order to discuss policies before actions were taken.
The events surrounding the Louisiana Purchase show the significance of change, and highlight the issue of an evolving government. Two important constitutional issues were raised by the Louisiana Purchase,