The country's formative years saw three strong leaders who established the tradition of personal rule that lasted until 1989: Jose Gaspar Rodriguez de Francia, Carlos Antonio Lopez, and his son, Francisco Solano Lopez. The younger Lopez waged a war against Argentina, Uruguay, and Brazil (War of the Triple Alliance, 1864-70) in which Paraguay lost half its population; afterward, Brazilian troops occupied the country until 1874. A succession of presidents governed Paraguay under the banner of the Colorado Party from 1880 until 1904, when the Liberal party seized control, ruling with only a brief interruption until 1940.

In the 1930s and 1940s, Paraguayan politics were defined by the Chaco war against Bolivia, a civil war, dictatorships, and periods of extreme political instability. Gen. Alfredo Stroessner took power in May 1954. Elected to complete the unexpired term of his predecessor, he was re-elected president seven times, ruling almost continuously under the state-of-siege provision of the constitution with support from the military and the Colorado Party. During Stroessner's 35-year reign, political freedoms were severely limited, and opponents of the regime were systematically harassed and persecuted in the name of national security and anticommunism. Though a 1967 constitution gave dubious legitimacy to Stroessner's control, Paraguay became progressively isolated from the world community.

On February 3, 1989, Stroessner was overthrown in a military coup headed by Gen. Andres Rodriguez. Rodriguez, as the Colorado Party candidate, easily won the presidency in elections held that May, and the Colorado Party dominated the Congress. In 1991 municipal elections, however, opposition candidates won several major urban centers, including Asuncion. As president, Rodriguez instituted political, legal, and economic reforms and initiated a rapprochement with the international community.

The June 1992 constitution established a democratic system of government and dramatically improved protection of fundamental rights. In May 1993, Colorado Party candidate Juan Carlos Wasmosy was elected as Paraguay's first civilian president in almost 40 years in what international observers deemed fair and free elections. The newly elected majority-opposition Congress quickly demonstrated its independence from the executive by rescinding legislation passed by the previous Colorado-dominated Congress. With support from the United States, the Organization of American States, and other countries in the region, the Paraguayan people rejected an April 1996 attempt by then-Army Chief Gen. Lino Oviedo to oust President Wasmosy, taking an important step to strengthen democracy.

Oviedo became the Colorado candidate for president in the 1998 election, but when the Supreme Court upheld in April his conviction on charges related to the 1996 coup attempt, he was not allowed to run and remained in confinement. His running mate, Raul Cubas Grau, became the Colorado Party's candidate and was elected in May. The assassination of Vice-President Luis Maria Argana and the killing of eight student anti-government demonstrators, allegedly carried out by Oviedo supporters, led to Cubasí resignation in March 1999. The President of the Senate, Luis Gonzalez Macchi, assumed the presidency and completed Cubasí term. Gonzalez Macchi offered cabinet positions in his government to senior representatives of all three political parties in an attempt to create a coalition government that proved short-lived. Gonzalez Macchiís government suffered many allegations of corruption, and Gonzalez himself was found not guilty in a Senate impeachment trial involving corruption and mismanagement charges in February 2003.

In April 2003, Colorado candidate Nicanor Duarte Frutos was elected president. He was inaugurated on August 15. Duarteís administration has focused upon attacking corruption and improving the quality of management, in the wake of the Gonzalez administration, widely considered the most corrupt in the post-Stroessner era. Duarte has been successful at working constructively with an opposition-controlled Congress, and in his first year of office, six Supreme Court justices suspected of corruption were removed from office, and major tax reforms were enacted. Macroeconomic performance has improved significantly under the Duarte administration, with inflation falling significantly, and the government clearing its arrears with international creditors. Unemployment remains stubbornly high and the living standard of most households has not improved. The administration has placed a strong emphasis on participating in international institutions and has used diplomacy to promote the opening of international markets to Paraguayan products. In June 2004, Oviedo returned to Paraguay from exile in Brazil and was imprisoned for his 1996 coup-plotting conviction.