The Social Liberal or Radical Left Party was one of the original parties in Janda's 1950-1962 ICPP study. The party continued throughout 1950-1990 in the Harmel-Janda study of party change in Denmark, Germany, the U.K. and U.S.

The essay on party politics in Denmark from 1950 to 1962 says:

In the late 1960s and early 1970s, the Radical Liberals (Radical Venstre) enjoyed a doubling of their parliamentary strength to about 15 percent of the seats, and the party headed a governmental coalition in 1968-1971. But the party's support fell sharply afterward to about 4 percent of the votes and seats.

The essay on party politics in Denmark from 1963 to 2000 says:

One of the four old parties, the RV's support remained around the five percent plateau after the original ICPP period, with the notable exception of the 15 percent it won in 1968 and held through 1973. During the 1968-1971 period, the RV formed a governing coalition with the Liberal Party (V) and the Conservative People's Party (KF) after a period of absolute socialist majority in the legislature. After this period, the RV resumed its balancing strategy between socialist and non-socialist blocs: the party joined the 1988-1990 KF-V government, after which they joined the government led by the Social Democratic Party (SD) from 1993-1994. Though a small party, the RV has used its pivotal position to influence both the moderate left and right parties, and to oppose the more extreme leftist and rightist parties.

Consult the index to variables for annual scores of the party's issue orientation, organizational complexity, centralization of power, and coherence from 1950 through 1990.