Except for an initial period of political disorder, independent Chile's first century of political life was dominated by the aristocratic Liberal and Conservative parties. Segments of the two parties split, shifted, entered into new alliances, regrouped, and took on new names. Since electoral law permitted the registration of parties with relatively small popular bases, coalitions were usually formed to elect presidents and control the Congress. Many cabinets had a fleeting existence. After 1860, the Radicals emerged from the Liberal party, and over the next six decades, they increased their following with the rise of the middle class. In the meantime, the Liberals became conservative, and moved close to that party. Although the Conservatives and Liberals disagreed over the status of the Roman Catholic Church and over the matter of relative congressional and presidential powers, they were united in opposing the Radicals.
Designation of Chilean parties as being of the right, center, or left has been a function of shifting national political climates. Parties and party alliances have tended to appear and disappear over time. During the 1950s and 1960s, there were fewer, but much larger parties. Before the 1973 military coup there were five major parties in Chile: the Christian Democratic Party, founded in 1957, the Socialist Party, founded in 1931, the Communist Party, founded in 1921 (and outlawed during 1948–58), the National Party, formed in 1966 by members of the Liberal and Conservative parties, and the old Radical Party, which saw its strength greatly diminished after 1964. The ruling Allende coalition of Popular Unity consisted of Socialists, Communists, and several smaller leftist parties. The most radical political group, the Revolutionary Movement of the Left, was not a coalition member.
In September 1973, all the Allende coalition parties were abolished. The other parties were initially suspended and then banned in March 1977.
The reemergence of political parties in the aftermath of Pinochet's ouster was dramatic. In 1990, to ensure that Pinochet's preferred presidential candidate would not take office, several center-left parties came together as the Coalition of Parties for Democracy (Concertación) and backed a single candidate. Today, the coalition includes four major parties: the Christian Democrats (PDC), the Party for Democracy (PPD), the Radical Party (PR), and the Socialist Party (PS). The Concertación has won three consecutive presidential elections, four consecutive parliamentary elections and three consecutive municipal elections, becoming the most successful and lasting political coalition in Chile's history. The opposition from the right comes from the Independent Democratic Union (UDI), and the National Renewal (RN), which, bolstered by the influence of most Senate appointees (including 4 former military generals) have held sway in the Senate.