Republicanism is the political theory that holds that the best form of government is a republic.
The term republic most commonly means the system of government in which the head of state is elected for a limited term, as opposed to a constitutional monarchy. Republicanism in this sense is support for the abolition of constitutional monarchies. This sense is particularly important in countries such as Australia, where the abolition of the monarchy is a major political issue; and also countries such as the United Kingdom, where republicanism has never experienced much popular support, but nonetheless has been a significant minority position.
Another, older and less commonly used definition of the term, uses the term "republic" to describe what is more commonly called a representative democracy; it restricts the term "democracy" to refer only to direct democracy. See democracy for further discussion of this term usage and its history.
Republicanism in the United States
According to the older definition of the term, the United States of America is a republic, not a democracy. (Although most people, including most Americans, call it a democracy, they are using the modern definition, not the older one referred to here). This usage of the term republic was particularly common around the time of the American Founding Fathers. The authors of the U.S. Constitution intentionally chose what they called a republic for several reasons. For one, it is impractical to collect votes from every citizen on every political issue. In theory, representatives would be more well-informed and less emotional than the general populace. Furthermore, a republic can be contrived to protect against the "tyranny of the majority." The Federalist Papers outline the idea that pure democracy is actually quite dangerous, because it allows a majority to infringe upon the rights of a minority. By forming what they called a Republic, in which representatives are chosen in many different ways (the President, House, Senate, and state officials are all elected differently), it is more difficult for a majority to control enough of the government to infringe upon a minority.
Republicanism in Northern Ireland
The term "republican" is used in Northern Ireland to refer to nationalist groups such as the Irish Republican Army and their political wing Sinn Fein who support violence as a means of establishing a republic (in the more common sense) encompassing the whole of the island of Ireland. This is in contrast to democratic nationalist groups such as the Social Democratic and Labour Party (SDLP). During the decades of the The Troubles the democratic nationalist have had more support than the republicans among the minority Catholic electorate. With the recent, albeit shaky, development of a peace process, Sinn Fein's move away from violence has resulted in increased support and in the recent elections they received slightly more votes than the SDLP.
Republicanism can also mean the doctrines of the Republican Party of the United States.