Predecessor seats

Blaenau Gwent incorporates most of the area of Aneurin Bevan's old constituency and other areas as population expansion has been low or negative following the 1960s. The constituency was created in 1983, twenty-three years after Bevan's death, from the upper part of the former Abertillery constituency, the town of Brynmawr from Brecon and Radnor, and Bevan's old Ebbw Vale seat with the exception of the area of the Rhymney Community (formerly Rhymney Urban District). The then-Labour party leader Michael Foot, who had won Ebbw Vale in the by-election following Bevan's death, was the seat's first MP.

Strong Labour Party majorities

Until 2005, the constituency statistically ranked in the top 20 safest Labour seats in the country by size of majority and by continuous representation by candidates from that party. In the 1983 and 1992 general elections, it was Labour's safest seat.

In the 2010 general election, Labour candidate Nick Smith gained the seat with a 29.2% swing from Independent back to Labour; as one of three seats Labour gained in that election where its government fell. The 2015 result made the seat the 30th safest of Labour's 232 seats by percentage of majority.^[6]

Period of independent representation

At the 2005 general election, the Labour Welsh Assembly Member Peter Law ran as an independent and won the seat. He had resigned from the Labour Party in protest at the imposition of an all-women candidates' shortlist following the retirement of incumbent MP Llew Smith and he overturned a 19,313 (60%) Labour majority with a significant 9,121 (25%) majority. In 2006 the Labour Party decided not to require an all-women shortlist at the next general election.^[7]

Law died of a brain tumour on 25 April 2006, prompting a by-election in the seat on 29 June. Labour failed to regain the seat as Law's former campaign manager, Dai Davies, was elected to replace him, beating Owen Smith, the Labour candidate who later became MP for Pontypridd.

Opposition parties

The Conservative Party and Liberal Democrats have both been very weak in the seat. From 1987 until 2017 neither had ever won 10% of the vote and the Conservatives had never achieved one eighth of the total votes cast. However, in 2015 the Conservatives achieved just under 15% of the vote, with Plaid Cymru in second place after Labour. In 2005 the Liberal Democrats received their lowest share of the vote in the United Kingdom and the Conservatives their second lowest, and both lost their deposits, though this particular election saw unusual circumstances.

The 2010 result was one of few where an Independent candidate kept their deposit, winning in excess of 5% of the votes cast, and pushed one of the main three parties into fourth place; the independent Blaenau Gwent People's Voice group fielded no candidate in 2015. Three non-Labour candidates exceeded 5% of the vote (the deposit threshold) in 2015, the foremost locally being UKIP (who achieved nearly 18% of the vote), but the Lib Dem and Green candidates failed to retain their deposits.

Elections in the 1980s

Elections in the 1990s

Elections in the 2000s

Elections in the 2010s

Of the 35 rejected ballots:

• 25 were either unmarked or it was uncertain who the vote was for.^[26]
• 9 voted for more than one candidate.^[26]
• 1 had writing or mark by which the voter could be identified.^[26]

Of the 84 rejected ballots:

• 44 were either unmarked or it was uncertain who the vote was for.^[29]
• 30 voted for more than one candidate.^[29]
• 10 had writing or mark by which the voter could be identified.^[29]

This was the largest decrease in the Plaid Cymru vote share at the 2019 general election.^[31]