The county constituency was first created in 1885 from the southern part of Down. From the dissolution of Parliament in 1922, it was merged back into that constituency.
The seat was re-created in 1950 when the old Down two MP constituency was abolished as part of the final move to single member seats. Originally the seat consisted of most of the mid and southern parts of County Down, with the north included in North Down. Of the post 1973 districts, it contained all of Down and Banbridge, together with parts of Newry and Mourne, Ards and Craigavon.
In 1983 the seat was radically cut down as part of an expansion of Northern Ireland's constituencies from 12 to 17. Significant parts of the constituency were transferred to either Upper Bann or Newry and Armagh.
In boundary changes proposed by a review in 1995, the seat was originally to be abolished and replaced by a new Mid Down constituency. This provoked a storm of protest and following a local enquiry minor changes were made with the seat losing one small section to Lagan Valley and another to Strangford. It still consists of parts of Down, Banbridge and Newry and Mourne districts.
In 2005, the Boundary Commission published provisional recommendations for modifying the boundaries of constituencies in Northern Ireland. For South Down, it originally proposed to add part of Newry from Newry and Armagh and the Loughbrickland part of Banbridge district from Upper Bann, while losing some more of Down to Strangford. These changes were challenged in a round of public consultations, with the result that revised recommendations were made. Under the new proposals, the Newry area will remain in Newry and Armagh and Loughbrickland in Upper Bann. This means that only 4 wards around the town of Ballynahinch were transferred to Strangford. These changes became the final recommendations and were given legal effect in 2008.
The constituency was a predominantly Nationalist area in 1918. The Unionists had significant but minority support. The Sinn Féin candidate polled poorly, probably due to the limited electoral pact to avoid seriously splitting the anti-unionist vote in seats the unionist candidate might have otherwise won.
Sinn Féin contested the general election of 1918 on the platform that instead of taking up any seats they won in the United Kingdom Parliament, they would establish a revolutionary assembly in Dublin. In republican theory every MP elected in Ireland was a potential Deputy to this assembly. In practice only the Sinn Féin members accepted the offer.
The revolutionary First Dáil assembled on 21 January 1919 and last met on 10 May 1921. The First Dáil, according to a resolution passed on 10 May 1921, was formally dissolved on the assembling of the Second Dáil. This took place on 16 August 1921.
In 1921 Sinn Féin decided to use the UK authorised elections for the Northern Ireland House of Commons and the House of Commons of Southern Ireland as a poll for the Irish Republic's Second Dáil. This area, in republican theory, was incorporated in a potential eight-member Dáil constituency of Down.
When initially created this seat had a clear unionist majority, albeit with a strong nationalist minority. However boundary changes, which have wrapped it closer around nationalist heartlands near Downpatrick and the Mournes have transformed South Down into a safe nationalist seat.
The Westminster seat was consistently held by the Ulster Unionist Party from its creation until 1987. In the October 1974 general election the former Conservative MP Enoch Powell defended the seat for the UUP, representing a coup for them as they gained the support of a high profile English politician, offering them a spokesperson to the United Kingdom as a whole.
Powell advocated a policy of integration for Northern Ireland whereby all forms of devolution would be wound up and the province governed as an integral part of the United Kingdom. As part of this he campaigned for the province to have the same ratio of MPs to population as in the rest of the United Kingdom, rather than fewer, which had previously been justified due to the existence of the devolved Stormont Parliament. Powell was successful in this but a side effect was that in his own constituency a significant block of unionist voters were removed, resulting in a nationalist majority. Powell managed to survive due to a combination of a split nationalist vote and personal popularity in the Catholic community, but in 1987 he narrowly lost to Eddie McGrady of the Social Democratic and Labour Party who has held the seat to date.
Since then the unionist vote has declined further due to boundary changes, which excluded mainly unionist Dromore and Saintfield, and a trend for many unionists to vote for McGrady at Westminster elections. This is interpreted by the SDLP as genuine cross-community support and by unionist parties as tactical voting.
Although votes for Sinn Féin have recently increased in the constituency, the SDLP is currently significantly ahead and look likely to retain the seat for the foreseeable future.
The Member of Parliament since the 1987 general election is Eddie McGrady of the Social Democratic and Labour Party. He defeated Enoch Powell of the Ulster Unionist Party who had represented the seat since October 1974.
|1885||John Francis Small||Irish Parliamentary|
|1886||Michael McCartan||Irish Parliamentary|
|1892||Irish National Federation|
|1902||Jeremiah McVeagh||Irish Parliamentary|
|1922||constituency abolished - see Down|
|1950||Lawrence Orr||Ulster Unionist|
|1974||Rt Hon. Enoch Powell||Ulster Unionist|
|1987||Eddie McGrady||Social Democratic and Labour|
At the 1900 UK general election, Michael McCartan was elected unopposed.