The Socialist People's party, founded in 1958, appeared too late to qualify as one of the original parties in Janda's 1950-1962 ICPP study. It continued throughout 1950-1990 and qualified for 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:

The Socialist People's Party was formed in 1958 by former Communists who split from the party after the Hungarian revolt. The party hovered between 5 and 10 percent of the seats, with some evidence of recent decline.

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

The SF was founded by former Communist Party leader Aksel Larsen, who was expelled for taking an autonomous route from Moscow. Though the SF has never participated in cabinet, it supported the minority Social Democratic Party (SD) government from the outside in the 1966-1968 period when there was a socialist majority in the legislature, in what became known as "the red cabinet." Though the SD formed a minority government in a similar situation from 1971-1973, it was supported by the center and right in its negotiations for European Community membership against SF opposition (Thomas and Oakley, 1998: 385-386). The party's support waxed in the 1980s, with its legislative clout rising as high as 15 percent of the seats in 1987. Its strength waned somewhat in the 1990s, however, dropping to a seven to nine percent plateau.

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.