The seat has been relative to others a marginal seat since 2015 as its winner's majority has not exceeded 4.2% of the vote since the 29.9% majority won in that year. The seat has changed hands once since that year.
It has returned a Labour MP for the first time since its first election in 1885 and, apart from a brief period between 1916 and 1918, was held by the Conservatives from 1885 until 1997, when the Liberal Democrats won it. This long period of Conservative dominance included all 3 elections under Margaret Thatcher's premiership, starkly contrasting with the consensus within most seats in the county and the other county which Sheffield Hallam borders, Derbyshire.
In a 2013 survey by The Campaign to End Child Poverty, Sheffield Hallam was found to be the constituency with the lowest level of child poverty in the UK, at under 5%.
On income-based 2004 statistics, this is the most affluent constituency one place below the top ten seats of the 650, which were spread across the South East of England (including London), with almost 12% of residents earning over £60,000 a year. This measure placed Sheffield Hallam above Windsor and Twickenham.
Based on 2011–12 income and tax statistics from HMRC, Sheffield Hallam has the 70th highest median income of the 650 parliamentary constituencies, with those above it almost exclusively in London and the South East, and placing it above Tunbridge Wells (76th), The Cotswolds (92nd), Cambridge (97th), Hemel Hempstead (103rd), and David Cameron's former Witney constituency (121st).
The 2001 Census showed Hallam to have the highest number of people classified as professionals of any of the UK constituencies. Furthermore, 60% of working age residents hold a degree, 7th highest and exceeding Cambridge.[n 2]
The majority of Hallam is rural, spreading in the west into the Peak DistrictNational Park. It also contains some of the least deprived wards in the country, has low unemployment (1.5% jobseekers claimants in November 2012) and a high rate of owner occupancy with few occupants who rent their home. Since the 2010 boundary changes, neither of Sheffield's universities have a campus in the constituency but it still includes areas where many students live.
In the 2017 general election, the Labour party candidate, Jared O'Mara, won the seat from Clegg. This was the first time in the seat's history that it has returned a Labour MP.
From 25 October 2017 until 3 July 2018, O'Mara had the whip withdrawn as a Labour MP and sat as an independent. It was later restored but he quit the Labour Party shortly afterwards. but resigned from the party nine days later. He now sits as an independent MP.
Prior to its creation Hallam was a part of the larger Sheffield Borough constituency, which was represented by two Members of Parliament (MPs). In 1885 the Redistribution of Seats Act, which sought to eliminate constituencies with more than one MP and for the first time allow approximately equal representation of the people, led to the break-up of the constituency into five divisions: each represented by a single MP, as today. Hallam was one of these new divisions. Its first MP, the Conservative Charles Stuart-Wortley, had previously been an MP in the Sheffield constituency, elected for the first time in 1880.
Hallam was regarded in 2004 as the wealthiest constituency in the north of England and was held by the Conservative Party for all but two years from 1885 to 1997. At the 1997 general electionRichard Allan of the Liberal Democrats took the seat with an 18.5% swing, becoming only the second non-Tory ever to win it. He handed the seat to fellow Lib Dem Nick Clegg in 2005, who held it until his defeat by Labor's Jared O'Mara in 2017.
At the 2017 General Election the constituency recorded its highest turnout since 1951, with 77.8% of voters going to the polls.
Constituency polls during the 2010–2015 Parliament
Due in part to the high profile of the constituency's then-MP Nick Clegg, who served as Deputy Prime Minister during the 2010–15 Parliament, Sheffield Hallam is unusual in having had seven constituency-specific opinion polls conducted between 2010 and 2015. Each of these polls suggested significant changes in the vote share compared to 2010 general election. The first poll, in October 2010, suggested a drop in the Lib Dem lead in the seat to just 2%, from nearly 30% at the general election five months earlier. Five of the six remaining polls, which appeared between May 2014 and May 2015, suggested that Labour was in the lead in the seat by this time, with the Labour lead fluctuating to between 1% and 10%, and one put the Lib Dems in the lead. On average across all seven opinion polls, Labour had a lead over the Lib Dems of 2.5%. The Conservatives came second in one poll, and third in the other six polls. It should be noted that the May 2015 ICM poll scores displayed are those of the constituency voting intention question. The same poll also carried the standard voting intention question, which showed a Labour lead.
In 2010, Sheffield Hallam was one of a number of constituencies which experienced problems on polling day leading to some people being unable to cast their vote. In this case, voters at the Ranmoor polling station were subjected to long queues and some voters were turned away when polls closed at 10 pm, with Liberal Democrat candidate Nick Clegg apologising to those voters affected. Acting Returning Officer John Mothersole said that staff had been "caught out" by a high turnout, and the Electoral Commission instigated a review of procedures in Hallam and other constituencies where similar problems had occurred.
^At the 1997 general election the seat saw an unprecedented 18.2% one-party swing from the other parties, particularly the large Conservative vote, towards the Liberal Democrat winning candidate.
^After 28 years as MP for the seat, John Osborn stood down at the 1987 general election. His replacement as the Conservative Party candidate, local businessman Irvine Patnick, held the seat for the Conservatives with a slightly reduced majority.