Constitutional Assembly elections were held in the recently proclaimed Kingdom of Serbs, Croats and Slovenes (later renamed Yugoslavia) on 28 November 1920. The election was held in the context of political debate over the degree of centralisation or potential federalisation of Yugoslavia. The election was held in the entire territory of the country except the areas obtained shortly beforehand through the Treaty of Rapallo which regulated the borders with Italy because those areas were still under Italian occupation. The election legislation was enacted by the Temporary National Representation, a representative body appointed after creation of Yugoslavia. The legislation prescribed the universal manhood suffrage, except for Hungarian and German minorities, certain former Ottoman Empire nationals and Jews.

A total of 22 political parties or groups fielded candidates in 55 electoral districts which were determined based on pre-First World War censuses. Varying degrees of wartime losses and the suffrage regulations led to significant differences in the number of registered voters per parliamentary seat. There was a 65% voter turnout for the election. None of the parties won a majority of the 419 seats available. The Democratic Party (DS) and the People's Radical Party (NRS) emerged as the largest factions, winning 92 and 91 seats respectively. The third-most successful party at the election was the Communist Party of Yugoslavia (KPJ), winning 58 seats, followed by the Croatian Peasant Party (HSS) receiving 50 seats. The HSS was the only party to win an absolute majority in any province. Thus it became the leading Croatian political party.

The DS-NRS government failed to secure the needed majority in the assembly that would support the adoption of its draft constitution. The government therefore sought and obtained support from the Yugoslav Muslim Organization, the Džemijet, and a faction of the Agrarian Party in exchange for favourable terms of the pending land reform in interwar Yugoslavia. These alliances, aided by the government-determined rules of order of the Constitutional Assembly requiring a simple majority of all members of the assembly, led to the adoption of the Vidovdan Constitution as the first Yugoslav constitution. The DS and the NRS positions were brought closer together in the struggle against anti-centralist parties.

The rule requiring only the simple majority of votes was opposed by the parties whose objective was to prevent the centralisation of Yugoslavia. The HSS and other Croatian parties claimed that the Corfu Declaration agreed on by the Kingdom of Serbia and the Yugoslav Committee in 1917 required a qualified majority. They expected the constitution to be adopted by a two-thirds majority, and the Croats perceived the government-adopted rules as a betrayal. Subsequently, the HSS decided not to take part in the Constitutional Assembly and declared its position that the constitution would not be binding for Croats or Croatia. The KPJ attracted a significant protest vote, and a series of KPJ-led protests prompted the government to issue Obznana decree significantly curbing KPJ activities. In turn, the KPJ also left the parliament before the constitution was voted on. The Slovene People's Party left the assembly soon after.

Background The Kingdom of Serbs, Croats and Slovenes (later renamed Yugoslavia) was proclaimed by Prince Regent Alexander on 1 December 1918. The proclamation was made following a request by a delegation of the National Council of Slovenes, Croats and Serbs, representing the South Slavs living in territories once belonging to Austria-Hungary. The delegation received instructions requiring the establishment of a federation, but the delegation ignored the instructions. Following the proclamation, the Prince Regent appointed a government consisting of the Serb-dominated centralist parties, specifically the Democratic Party (DS) and the People's Radical Party (NRS). The Prince Regent appointed and confirmed subsequent governments. Before the 1920 election, the cabinet of Milenko Vesnić was appointed. It was replaced by the Nikola Pašić cabinet before the Constitutional Assembly was convened. The Temporary National Representation was established as an interim parliament, which primarily consisted of appointed members. The Temporary National Representation was meant to enact electoral law for the future Constitutional Assembly.

By the time of proclamation of Yugoslavia, the system of government in the state was largely undecided. Representatives of the Kingdom of Serbia and the Yugoslav Committee, an ad-hoc group claiming to represent the South Slavs living in Austria-Hungary, had agreed in the 1917 Corfu Declaration that Yugoslavia would be a monarchy with the House of Karađorđević as its head, with the question of the level of centralisation to be decided later on. In November 1918, representatives of the Yugoslav Committee, joined by the National Council of Slovenes, Croats and Serbs, negotiated with the representatives of Serbia on the question of centralisation. This council produced the Geneva Declaration, an agreement that Yugoslavia would be a confederation with a central government with limited powers. The Serbian government rejected this agreement because it wanted to establish a more centralised state serving Serbian political interests better.

Another issue was the Adriatic question, that is, the uncertainty regarding the borders of Yugoslavia. This arose from Italian claims based on the 1915 Treaty of London and the Fiume question, and was not addressed before the 1920 Treaty of Rapallo. The terms of the treaty were not fulfilled immediately. Instead, the Allied occupation of the eastern Adriatic, including the region of Dalmatia, remained in place until September 1921.

Electoral system

The Temporary National Representation adopted the Election Act on 2 September 1920. The election law prescribed the universal suffrage for men over the age of 21 who were enrolled in the voter register. The law restricted the voting right to nationals of Serbia or Montenegro before 1 December 1918, citizens of Croatia-Slavonia or Dalmatia, and residents of Bosnia and Herzegovina and other territories included in Yugoslavia. The law also gave the right to vote to other Slavs residing in Yugoslavia, effectively numerous refugees from Russia, but also confirmed the right of Slavic and Albanian minorities to vote.

Ethnic Germans, Italians, and Hungarians living in Yugoslavia were not allowed to vote. The same applied to former Ottoman nationals, who had been residents in territories that became Yugoslav and left before November 1915. Furthermore, the right to vote was denied to the Jews unless they declared themselves Serbs or Croats or if the local authorities deemed them Serbs or Croats. Yugoslav authorities claimed that state security concerns justified the denial of voting rights. The denial of the right to vote was in breach of the obligations Yugoslavia assumed under the Treaty of Saint-Germain-en-Laye. The voting rights were also denied to convicted prisoners, people stripped of their civil rights, and certain religious minorities such as Jehovah's Witnesses. The legislation also determined the method of compilation of electoral registers, specifying that one had to reside in a particular place for six months to be admitted to the register.

Candidates had to be eligible to vote, literate, permanently residing in Yugoslavia for at least ten years, and over 25. A candidate was allowed to stand in election in up to three different districts simultaneously and, if successful in multiple districts, had to pick one and withdraw in others. Candidate lists were put forward for each electoral district, needing a hundred endorsements to be valid. Candidates having university-level or equivalent education to be "qualified candidates". The law required the ratio of qualified to ordinary candidates in each district to be at least 1:4, with at least one candidate in the list being qualified.

Voters cast secret ballots. Using rubber balls dropped into the appropriate boxes, voting was performed to indicate support for a specific candidate or candidate list. The method was adopted from Serbian pre-war electoral law, selected to accommodate many illiterate voters.

Electoral districts There were 55 electoral districts nationwide, defined differently depending on the province. Southern Serbia (corresponding primarily to present-day Kosovo and Northern Macedonia) and Bosnia and Herzegovina were used as the electoral districts in Serbia. In Croatia-Slavonia, the county borders determined the electoral districts. In Vojvodina (consisting of Bačka, Banat, and Baranja), Slovenia and Dalmatia judicial districts were the basis for the electoral districts. Montenegro was a single electoral district. Major cities, like Belgrade, Zagreb, and Ljubljana, were placed in special urban districts to avoid having numerous rural voters in districts containing urban centres. The large cities were awarded a disproportionately high number of seats in the parliament compared to other parts of the country, and the number of registered voters per candidate varied there as well: there were 2,737 registered voters per candidate in Belgrade, but 4,954 in Zagreb.

The number of candidates in each district was determined based on the 1910 census as one candidate per 30,000 residents. An additional candidate was assigned if there were 17,000 or more left without a candidate. The number of registered voters per candidate also varied between the provinces. This ranged from 3,301 in Vojvodina to 8,092 in Dalmatia. These discrepancies resulted from using the prewar census to establish the number of candidates. They were explained as compensation to Serbia for its wartime losses. (During the war, Serbia lost a third of its male population while Croatia's population rose significantly.)

+Electoral districts by province Province Districts (seats) Bosnia and Herzegovina 6: Banja Luka (13), Bihać (8), Mostar (9), Sarajevo (10), Travnik (9), Tuzla (14) Croatia-Slavonia 9: Bjelovar-Križevci (11), Varaždin-Međimurje (13), Virovitica (9), Zagreb (17), Lika-Krbava (7), Modruš-Rijeka (8), Požega (9), Syrmia (14), City of Zagreb (5) Dalmatia 1: entire province (11) Montenegro 1: entire province (10) Serbia 18: Belgrade (5), Valjevo (5), Vranje (9), Kragujevac (6), Krajina (4), Kruševac (6), Morava (7), Niš (7), Pirot (4), Podrinje (8), Požarevac (9), Rudnik (3), Smederevo (5), Timok (5), Toplica (4), Užice (5), Čačak (5), City of Belgrade (6) Southern Serbia 12: Bitola (8), Bregalnica (3), Zvečan-Raška (5), Kosovo (6), Kumanovo (5), Metohija (3), Ohrid (3), Prizren (4), Prijepolje (4), Skopje (5), Tetovo (5), Tikveš (4) Slovenia 3: Maribor-Celje (21), Ljubljana-Novo Mesto (15), City of Ljubljana (4) Vojvodina 5: Velika Kikinda-Veliki Bečkerek (10), Pančevo-Bela Crkva (9), Subotica (8), Novi Sad (8), Sombor-Baranya (9)

+Registered voters per assembly seat per province Province Seats Registered voters per seat Bosnia and Herzegovina637,495 Croatia-Slavonia936,849 Dalmatia118,092 Montenegro104,337 Serbia1035,662 Southern Serbia555,600 Slovenia405,381 Vojvodina443,301

Campaign