San Marino was originally led by the Arengo, initially formed from the heads of each family.
In the 13th century, power was given to the Great and General Council. In 1243, the first two Captains Regent were nominated by the Council. As of 2010, this method of nomination is still in use.
The legislature of the republic is the Grand and General Council (Consiglio grande e generale).
The Council is a unicameral legislature with 60 members. There are elections every five years by proportional representation in all nine administrative districts. These districts (townships) correspond to the old parishes of the republic.
Citizens 18 years or older are eligible to vote. Beside general legislation, the Grand and General Council approves the budget and elects the Captains Regent, the State Congress (composed of ten Secretaries with executive power), the Council of Twelve (which forms the judicial branch during the period of legislature of the Council), the Advising Commissions, and the Government Unions.
The Council also has the power to ratify treaties with other countries. The Council is divided into five different Advising Commissions consisting of fifteen councillors who examine, propose, and discuss the implementation of new laws that are on their way to being presented on the floor of the Council.
Every six months, the Council elects two Captains Regent to be the heads of state.
The Regents are chosen from opposing parties so that there is a balance of power. They serve a six-month term.
The investiture of the Captains Regent takes place on 1 April and 1 October in every year. Once this term is over, citizens have three days in which to file complaints about the Captains' activities.
If they warrant it, judicial proceedings against the ex-head(s) of state can be initiated.
The practice of multiple heads of state, as well as the frequent re-election of the heads of state, are derived directly from the customs of the Roman Republic.
The Council is equivalent to the Roman Senate; the Captains Regent, to the consuls of ancient Rome.
San Marino is a multi-party democratic republic.
Due to a new election law in 2008 which raised the threshold for small parties entering Parliament, political parties in San Marino are organised into two opposing alliances: the right-wing Pact for San Marino, led by the San Marinese Christian Democratic Party; and the left-wing Reforms and Freedom, led by the Party of Socialists and Democrats, a merger of the Socialist Party of San Marino and the former communist Party of Democrats).
The Sammarinese general election, 2008 was won by the Pact for San Marino with 35 seats in the Grand and General Council against Reforms and Freedom's 25.
On 1 October 2007, Mirko Tomassoni was elected as one of the heads of state, making him the first disabled person ever to have been elected as captain regent.
San Marino is an associated state of Italy, which is responsible for its defense and which provides it an annual subsidy.