Question: What type of group does Lincoln by-election, 1973 and Democratic Labour have in common?

Context articles: Democratic Labour Party (UK)
Christchurch East by-election, 1943
Prague Conference
Lincoln by-election, 1973
Social Democratic Labour Party of Norway
Albert Gomes
Sleaford and North Hykeham by-election, 2016
Democratic Labour
People's Democratic Party (Trinidad and Tobago)
Yakov Zevin

The Democratic Labour Party was a small British left-wing political party in Walsall, sometimes known as the Walsall Democratic Labour Party.
 It was founded as a breakaway from the Labour Party after left-wing members were expelled in the mid-90s.
The 1943 Christchurch East by-election held on 6 February was caused by the death of Tim Armstrong during the term of the 26th New Zealand Parliament.
 The by-election in the Christchurch East electorate was contested by five candidates, including representatives from the Labour Party, the Labour breakaway party Democratic Labour Party and the National Party.
 The election was won by the Labour candidate, Mabel Howard, and started her long parliamentary career, which included her becoming the first female cabinet minister in 1947.
The Prague Conference, officially the 6th All-Russian Conference of the Russian Social Democratic Labour Party, was held in Prague, Austria-Hungary on 5–17 January 1912.
 Eighteen Bolsheviks attended, although Joseph Stalin and Yakov Sverdlov, who were in exile at the time, were not able to.
 Georgi Plekhanov claimed he was too ill to attend.
 At the conference, Vladimir Lenin and his supporters broke away from the rest of the Russian Social Democratic Labour Party and formed their own, Russian Social Democratic Labour Party (bolsheviks).
 The conference was meant to be secret; Lenin had instructed: "No-one, no organisation must know about this".
 However, every detail was known to the Okhrana, the secret police of the Russian Empire.
The Lincoln by-election of 1 March 1973 saw the re-election of Dick Taverne as Member of Parliament for Lincoln as a Democratic Labour representative, after Taverne's pro-Common Market views saw him repudiated by the Lincoln Constituency Labour Party.
 The by-election led to considerable speculation, stoked by Taverne, about the formation of a new centre party, but Taverne was unable to make his victory last.
The Social Democratic Labour Party of Norway (in Norwegian "Norges Socialdemokratiske Arbeiderparti") was a Norwegian political party in the 1920s.
 Following the Labour Party's entry into the Comintern in 1919 its right wing left the party to form the Social Democratic Labour Party in 1921.
 At the party convention in 1923, however, the Labour Party withdrew from Comintern, and the Communist Party of Norway was formed by the minority, who continued its affiliation with Comintern and the Soviet Union until 1991.
 The Social Democratic Labour Party was absorbed into the reorganised Labour Party in 1927.
Albert Maria Gomes (25 March 1911 – 13 January 1978), a Trinidad and Tobago unionist, politician, and writer of Portuguese descent, was the first Chief Minister of Trinidad and Tobago.
 He was the founder of the Political Progress Groups and later led the Party of Political Progress Groups.
 He was active in the formation of the Democratic Labour Party (DLP) in Trinidad and Tobago and played a role in forcing Sir Alexander Bustamante out of the Federal Democratic Labour Party.
 Gomes briefly led DLP in 1960 when factions loyal to briefly ousted Rudranath Capildeo after Capildeo left Trinidad and Tobago to take up a position at the University of London.
 However, the rank and file of the party stood behind Capildeo and Gomes left the party.
The Sleaford and North Hykeham by-election was a by-election in England for the House of Commons constituency of Sleaford and North Hykeham held on 8 December 2016.
 It was triggered by the resignation of Conservative MP Stephen Phillips on 4 November 2016.
 It was the first by-election to be contested in Lincolnshire since the Lincoln by-election of 1973 which by coincidence back then also saw the UK's relationship with Europe being a major issue.
Democratic Labour was a minor political party operating in the United Kingdom in the 1970s.
 They were formed by the Labour MP, Dick Taverne when his Constituency Labour Party (Lincoln) asked him to stand down as their candidate at the next general election.
 He had fallen out with them over Britain's continued membership of the European Economic Community which he supported but they did not.
The People's Democratic Party was a political party in Trinidad and Tobago.
 Under the leadership of Bhadase Sagan Maraj it contested the 1956 General Elections, capturing 5 of 24 elected seats in the Legislative Council and 20.3% of the vote.
 In 1957 it joined the Federal Democratic Labour Party and later co-founded the Trinidad and Tobago Democratic Labour Party, together with the Trinidad Labour Party and the Party of Political Progress Groups.
Yakov Davidovich Zevin (1888–1918) was a Jewish Communist activist, one of the Bolshevik Party leaders in Azerbaijan during the Russian Revolution.
 Zevin was born in Krasnapolle, a town in nowadays Mahilyow Voblast, Belarus.
 He became a member of Russian Social Democratic Labour Party in 1904 and he was arrested several times for conducting revolutionary activities.
 He was a delegate in the 6th (Prague) conference of the Russian Social Democratic Labour Party in 1912, where he represented the group of Mensheviks.
 After the conference he became close to the Bolshevik positions.
 In 1915 he was a member of the Baku committee of Bolsheviks.
 After the February Revolution of 1917 he worked in the Moscow council of working deputies.
 Zevin became one of the 26 Baku Commissars (he was the Commissar of Labor) of the Soviet Commune that was established in the city after the October Revolution.
 When the Commune was toppled by the Centro Caspian Dictatorship, a British-backed coalition of Dashnaks, SRs and Mensheviks, Zevin and his comrades were captured by British troops and executed by a firing squad between the stations of Pereval and Akhcha-Kuyma of Transcaucasian Railroad.