Alliance

Alliance chose Eric Bullick.^[11]

SDLP

The Social Democratic and Labour Party (SDLP) chose Patsy McGlone MLA for Mid Ulster, as their candidate.^[12]

Sinn Féin

Sinn Féin's Francie Molloy MLA, then deputy speaker of the Northern Ireland Assembly,^[13] was selected as the party's candidate.^[14][15]

Unionist unity

Nigel Lutton stood as an Independent Unionist, supported by the Democratic Unionist Party (DUP), the Ulster Unionist Party (UUP; who stood at the preceding general election as part of the Conservatives and Unionists), Traditional Unionist Voice (TUV) and others.

The possibility of a unionist 'unity' candidate to maximise the chance of defeating Sinn Féin was raised early on. There were discussions between the DUP and the UUP on standing a unity candidate.^[16] The UUP were described as being "coy" on whether or not they would stand or support another unionist candidate.^[4][17] The DUP chair of Magherafelt District Council and TUV leader Jim Allister MLA called for a unity candidate^[16][18] and TUV said they would probably not stand a candidate.^[19] The UUP leader Mike Nesbitt said in late January that the party would be willing to support a "community candidate", but that the UUP would stand a candidate if the DUP stood a candidate.^[20] However, a meeting of the UUP constituency association was reported to be divided on the issue of whether to support a unity candidate.^[20] This came against a backdrop of greater unionist unity in Northern Irish politics more generally, including the setting up of the Unionist Forum and warmer relationships between the DUP and UUP,^[21] and the flag protests.

On behalf of the UK Independence Party, David McNarry MLA also supported the idea of a unionist unity candidate in a press release.^[22]

The idea of a unionist unity candidate was criticised as "living in the past" by Molloy, the Sinn Féin candidate.^[23] Alliance candidate Eric Bullick also criticised the decision.^[24]

On 14 February, the UUP and DUP constituency associations both agreed to support victims' campaigner and local undertaker^[25] Nigel Lutton as a single unionist candidate.^[26] TUV were also supporting Lutton's candidacy, with Walter Millar, the party's constituency chairman and their candidate at the general election, signing Lutton's nomination papers.^[27] However, two UUP Members of the Northern Ireland Legislative Assembly, former deputy leader John McCallister and Basil McCrea, resigned from the party in protest at the decision and closer co-operation with the DUP.^[11] After the by-election, in June 2013, they announced the formation of NI21, a new unionist party.^[28]

Lutton declined to tell reporters which party he usually votes for. He previously worked as a personal assistant for DUP MP David Simpson, to whom he is related, and had before that been a member of the Young Unionists, the youth wing of the UUP. His election agent was UUP General Secretary Colin McCusker, a long-time personal friend. Both DUP and UUP politicians were involved in his campaign.^[29]

Willie Frazer, a victims' campaigner, independent unionist and spokesman for the then newly constituted protest alliance the Ulster People's Forum, initially announced his intention to stand.^[4][30] Frazer told a 'webchat' for the Belfast Newsletter that the Ulster People's Forum "is not a political party", and that in usual circumstances he would consider voting for the Traditionalist Unionist Voice.^[31] At the end of January 2013, Frazer then said he would consider not standing in favour of Jamie Bryson, a leading figure in the Belfast City Hall flag protests who is the interim chair of the Ulster People's Forum.^[32] After Lutton's selection, Frazer initially announced that he would not be running and fully supported him.^[33] However, he later said he would still consider standing if Lutton was too close to the DUP.^[34] He did not, in the end, submit his candidacy. After the by-election, in April 2013, he co-founded the Protestant Coalition, a new political party.

Allegations about the killing of Frederick Lutton

Nigel Lutton's father, Frederick, was a former RUC reservist killed by the Provisional Irish Republican Army (PIRA) in 1979. In 2007, under Parliamentary privilege, DUP MP David Simpson (a cousin of Frederick Lutton) alleged that Francie Molloy, then a PIRA volunteer/member, was suspected by the police of being involved in Lutton's death. Simpson also claimed Molloy had become an informer for the British security forces after being caught in "a compromising position" and that he was "well known – and this information is from the police – for a series of sexual indiscretions". Molloy, the claims continued, allowed the police to "break open" the IRA's East Tyrone Brigade. These allegations were denied by Molloy,^{[11][35][36][37]} who has challenged unionists to repeat them outside Parliament, which would allow him to take legal action.^[38]

UUP leader Mike Nesbitt has said he was unaware of the allegations against Molloy when he agreed on the choice of Nigel Lutton as candidate.^[38] Nigel Lutton stated that his decision to stand was not because of Molloy's candidacy.^[25][39]