Cardiff South and Penarth has had three MPs since its creation, containing some very Labour-inclined wards from Cardiff such as Butetown, Grangetown and Splott, and several wards from the neighbouring borough of the Vale of Glamorgan, with Penarth mostly favourable to Labour, but some decent Conservative areas as Plymouth and Sully in the southern end of the seat. The first, elected at the 1983 general election, was the former Labour Prime Minister James Callaghan, who secured the seat with a 5.5% majority over Conservative David Tredinnick. Callaghan had immediately prior to the dissolution of Parliament, represented Cardiff South East. Callaghan first became an MP at the 1945 general election, for Cardiff South. The second MP was Alun Michael who served 25 years from 1987 before choosing to stand down in 2012. Michael's affiliation with the Co-operative Party did not appear on ballot papers at the 2010 general election because the Electoral Commission ruled that any joint candidates who wanted the names of both their parties included on the ballot paper could not also display the Labour red rose logo. Michael opted to drop the reference to the Co-operative Party but after the election denounced the ruling as "an outrageous piece of incompetence by the Electoral Commission". Michael briefly became Secretary of State for Wales in 1998. Michael held the seat at the 2010 general election with a majority of 10.6% following a 6% swing to the Conservative candidate. In 2012, Michael was selected by the Labour and Co-operative Parties as their candidate for the election of a Police and Crime Commissionerfor the South Wales Police force area and announced he would be standing down from Parliament. At a by-election held on 15 November 2012, Labour's decline was reversed coupled with very low turnout. Labour's Stephen Doughty succeeded Alun Michael winning 47.3% of the overall vote. This was an increase on Michael's 2010 performance. However, in terms of actual votes cast, it was Labour's lowest in this constituency. The 2015 result gave the seat the 83rd-smallest majority of Labour's 232 seats by percentage of majority. Labour's result in 2017 saw them secure their largest ever margin in the constituency in terms of raw votes. ;Other parties Five parties' candidates achieved more than deposit-retaining threshold of 5% of the vote in 2015. The second-placed candidate has been a Conservative since the seat was incepted. The closest result was in 1983, when Callaghan won by 5.5% of the vote. ;Turnout Turnout at general elections has ranged between 77.2% in 1992 and 56.2% in 2005.
Boundaries
1983–2010: The City of Cardiff wards of Butetown, Grangetown, Llanrumney, Rumney, Splott, and Trowbridge, and the Borough of Vale of Glamorgan wards of Alexandra, Cornerswell, Llandough, and Stanwell. 2010–present: The Cardiff electoral divisions of Butetown, Grangetown, Llanrumney, Rumney, Splott, and Trowbridge, and the Vale of Glamorgan County Borough electoral divisions of Cornerswell, Llandough, Plymouth, St Augustine's, Stanwell, and Sully.
