Frequently Asked Questions — Portsmouth South Constituency

Who won the Portsmouth South constituency election in 2015?

Conservative gained Portsmouth South constituency at the 7 May 2015 General Election, taking the seat from Labour. Conservative won with a majority of 5,241 votes (12.5%). Turnout was 58.5%.

What was the swing in Portsmouth South at the 2015 election?

The swing in Portsmouth South was 13.3% from LAB to CON — a modest shift towards CON. Swing is calculated using the Butler two-party formula: the average of the change in winner's vote share and the fall in the runner-up's vote share compared to the previous election here.

What does swing mean in UK elections?

Swing measures how much support has shifted between two parties compared to a previous election. The Butler swing formula — used in British election reporting since the 1950s — takes the average of the gain in the winner's vote share and the loss in the runner-up's. A 5% swing is considered large at ward level; anything above 10% is exceptional. The swing figure for Portsmouth South in 2015 is shown in the statistics above.