However, in practice, between 1936 and 1989, voters could vote against candidates preselected by the Communist Party only by spoiling their ballots, or by voting against the only candidate, whereas votes for the party candidates could be cast simply by submitting a blank ballot. Nohlen, D & Stöver, P (2010) Elections in Europe: A data handbook, p1642 ISBN 978-3-8329-5609-7 Carson, George Barr (1955). Electoral Practices in the U.S.S.R. F.A. Praeger. KOGAN, MICHAEL (2012). “SHAPING SOVIET JUSTICE: Popular responses to the election of people’s courts, 1948-1954”. Cahiers du Monde russe. 53 (1): 121–139. doi:10.4000/monderusse.9370. ISSN 1252-6576. JSTOR 23418027. Getty, J. Arch (1991). “State and Society under Stalin: Constitutions and Elections in the 1930s”. Slavic Review. 50 (1): 18–35. doi:10.2307/2500596. JSTOR 2500596 Jessen, Ralph; Richter, Hedwig, eds. (2011). Voting for Hitler and Stalin: Elections Under 20th Century Dictatorships. University of Chicago Press. ISBN 978-3-593-39489-3.
modlog to the rescue:
spoiler