Republicanism is a principle directly mentioned in the Constitution.

Article IV, Section 4:

The United States shall guarantee to every State in this Union a Republican Form of Government, and shall protect each of them against Invasion; and on Application of the Legislature, or of the Executive (when the Legislature cannot be convened) against domestic Violence.

These words are the 'Guarantee Clause' which imposes limitations on the type of government a state may have. The Clause requires the United States to prevent any state from imposing rule by monarchy, dictatorship, aristocracy, or permanent military rule, even through majority vote. Instead, governing by electoral processes is constitutionally required.

But what is it?

Prior to the 17th century, the term was used to designate any state, with the exception of tyrannical regimes. Derived from the Latin expression res publica (“the public thing”), the category of republic could encompass not only democratic states but also oligarchies, aristocracies, and monarchies. During the 17th and 18th centuries, the meaning of republic shifted with the growing resistance to absolutist regimes and their upheaval in a series of wars and revolutions, particularly the American Revolution (1775–83) and the French Revolution (1787–89). The term republic came to designate a form of government in which the leader is periodically appointed under a constitution, in contrast to hereditary monarchies.

Athough this would seem to mean a democratic state it has also be applied to authortarian regimes including military dictatorships such as the Republic of Chile under Augusto Pinochet and totalitarian regimes such as the Democratic People’s Republic of Korea.

As Benjamin Franklin emerged from Independence Hall at the close of the Constitutional Convention in September 1787, a woman approached and asked him what form of government the Convention had produced. Franklin responded, “A republic, madam—if you can keep it.”

He did not say 'a democracy, madam-if you can keep it' because democracy and republic are not strictly the same thing. In order to create a government based on the will of the many, with its legitimacy drawn from the people but also curb the excesses of majority rule a republic offered the best hope for the designers of the constitution.

What, then, is a republic? A republican government is one in which the people—directly or indirectly—are the ultimate source of authority, electing representatives to make laws that serve their interests and advance the common good. A constitutional republic, however, also limits the power of the majority through a framework that promotes competent government and affords protections for fundamental rights. This means limiting the power of government and limiting the power of the people. Benjamin Franklin observed that: “Democracy is two wolves and a lamb voting on what to have for lunch.” In forming a republic based in the sovereignty of the people but not the will of the people he hoped to promote justice and protect liberty,

The key features of the American Republic:

      • limited government

      • Separation of power

      • The Rule of Law

      • Entrenched rights

      • Popular sovereignty

The most basic feature of the American constitutional republic is the selection of representatives directly or indirectly by the people throughout all three branches of government, adhering to the principle that all power must flow from the people. While the direct election of representatives is reserved only for Congress, Americans indirectly choose the president (via the Electoral College) and all federal judges (via presidential appointment and approval of Senators, all of whom are now chosen by the people). Rule by the many is preserved as regular elections ensure the people maintain a constant voice in their government and remain the source of legitimate power.

Additionally, each branch represents distinctly different interests and is given specific powers and responsibilities that correlate with these interests. The legislative branch, for example, represents citizens (House of Representatives) and the states in which they reside (Senate), and is given the power to make law, raise taxes, declare war, and regulate commerce. The executive branch represents the interests of the nation, and as such is given the power to command the military, make treaties, and appoint ambassadors. Lastly, an example of judicial branch empowerment is through judicial review, to preserve the rule of law rooted in our Constitution and the laws enacted by Congress. This functional separation of powers is reinforced through a complex system of checks and balances that allows each branch to limit the reach and authority of the others serving to limit both passionate willfulness on the part of the people and the power of the government itself.

The Bill of Rights provides perhaps the clearest example of the dichotomy between a democracy and a republic. It is simultaneously the most celebrated feature of our “democracy” and the most anti-democratic feature of the constitutional republic. The Bill of Rights provides heightened protection for fundamental liberties, protecting both natural rights, such as freedom of conscience, and civil rights, such as protection against arbitrary search and seizure. Some rights can be confined if the government satisfies due process requirements. However, no matter how large the majority, one’s right to practice the religion of choice or to be free from arbitrary search by government officials cannot be abridged or simply voted away. Although popular sovereignty is preserved by the amendment process.

The Federalist No. 39, James Madison emphasizes popular sovereignty and majoritarian control as among the distinctive characters of the republican form:

We may define a republic to be, or at least may bestow that name on, a government which derives all its powers directly or indirectly from the great body of the people, and is administered by persons holding their offices during pleasure, for a limited period, or during good behavior. It is ESSENTIAL to such a government that it be derived from the great body of the society, not from an inconsiderable proportion, or a favored class of it; . . . It is SUFFICIENT for such a government that the persons administering it be appointed, either directly or indirectly, by the people; and that they hold their appointments by either of the tenures just specified.

In Federalist Paper 51, James Madison explains and defends the checks and balances system in the Constitution. Each branch of government is framed so that its power checks the power of the other two branches; additionally, each branch of government is dependent on the people, who are the source of legitimate authority.

In republican government, the legislative authority necessarily predominates. The remedy for this inconveniency is to divide the legislature into different branches; and to render them, by different modes of election and different principles of action, as little connected with each other as the nature of their common functions and their common dependence on the society will admit. It may even be necessary to guard against dangerous encroachments by still further precautions

''The United States is a republic, not a democracy.” This is one of those oft-repeated expressions that one hears in civil discourse whose meaning nevertheless remains somewhat fuzzy. The Founders understood that the public is the only legitimate sovereign of government. But it is not wholly democratic, in that they feared the abuse of that authority by the people and designed an instrument of government intended to keep temporary, imprudent, and intemperate outbursts of public opinion from dominating the body politic.

Their primary method of doing this was the separation of power across three branches of government. The public retains control over each branch, but the link between the people and each branch is conditioned by different factors. The House remains the most sensitive to public opinion, with representatives directly elected by the people to two-year terms. The president and Senate were originally intended to be less sensitive, with longer terms and mediating institutions (the Electoral College and state legislatures, respectively). Now, they are much closer to the public — with the Electoral College having become a nugatory pass-through for state plebiscites, and the Senate being directly elected by the people since the ratification of the 17th Amendment in 1913. The courts were to be the most immune of the branches to public opinion on a day-to-day basis, but, importantly, their composition and jurisdiction were to be determined by Congress and the president. And as an additional protection, a federal system was created whereby the national government possessed only enumerated powers, with the remainder of governing authority being explicitly retained by the states.