In everyday speech, most Americans use the word "constitution" as if it referred to the constitution of the United States adopted at the end of the eighteenth century, ratified and amended since then. It is connected in their minds with the word "citizens." There are no citizens except in republics, whether only some human beings have the suffrage or all are enfranchised.
What, then, is a constitution, either oligarchical and unjust or democratic and just? Aristotle's Politics, Book 1, Chapter 2, tell us that a constitution is an arrangement of political offices, designating the powers of the various offices and their responsibilities. A constitution determines who will be admitted to citizenship, how the other offices will be filled, and how the different offices should function in relation to one another.
The constitution maybe a written document, If so, the act by which the people adopt the constitution is an act prior to the existence of government. That fact raises an interesting question about Lincoln's dating of the birth of the United States in 1776 rather than 1791, when George Washington took office as the first President of the United States.
Another interesting question is whether there is constitutional government in the United Kingdom. The laws made and changed by Parliament give the government of the United Kingdom the appearance of a constitutionality, but unless government is constituted before it begins to function, the word "constitution" is ambiguously applied to governments with written and with legislatively enacted constitutions. The former is prior to the institution of government; the latter are posterior to the existence of government.
The most important feature of constitutional governments lies in the distinction between a government of men and a government of laws. When a human being govern by power which is able to exercise and which is vested in him or her personally, we have a despotic government, whether tyrannical or benevolent. But when those who govern not by their personal power, but by the power vested in the office they hold, assigned to that office by the constitution they swear to uphold, then the government is a government of laws. Constitutional governments can, in time, change, become less oligarchical and more democratic. The mode of amending constitutions must be prescribed by the constitution itself.
Office holders are not the governors in constitutional government, but rather the people who adopt and amend the constitution. It is they who, as citizens under the constitution, vote and elect those who administer the government.
The government resides in the power of the people who have been made citizens. The officeholders in Washington and elsewhere are its administrators. They are the servants of the people, We acknowledge that fact when, after national elections that change the party in office, we talk about a new administration, not a new government.