UK By-Elections 2024-2026
Every Westminster by-election since the July 2024 General Election - full results, swings and what they signal for 2029.
Why by-elections matter
By-elections occur when a sitting MP dies, resigns or is disqualified. Contested mid-Parliament, they consistently produce larger swings than general elections - voters feel less pressure to vote tactically and often use the contest to send a message to the government. The 2024-2026 by-election cycle has become a live laboratory for Reform UK's electoral viability, with the party converting strong polling into actual seats for the first time.
Full Results: All By-Elections 2024-2026
| Constituency | Date | Result | Lab % | Con % | Reform % | Green % | Key story |
|---|---|---|---|---|---|---|---|
| Kingswood | Feb 2024 | Lab hold | 35% | 27% | 14% | 7% | Labour held narrowly; Reform entered double figures in a solid Conservative seat |
| Wellingborough | Feb 2024 | Lab gain from Con | 47% | 24% | 13% | 4% | Massive Labour gain; Reform already emerging as major third force |
| Blackpool South | May 2024 | Lab hold | 48% | 17% | 17% | 5% | Reform matched Conservatives in a seaside town hit by coastal decline |
| Runcorn & Helsby | May 2025 | Reform gain | 33% | 11% | 38% | 5% | Historic: Reform UK first by-election win. Swing of 25+ points from Labour |
| Wigan | Oct 2025 | Lab hold (narrow) | 36% | 10% | 34% | 7% | Labour survived by just 3 points; Red Wall seat now genuinely marginal |
| Blyth & Ashington | Jan 2026 | Reform gain | 32% | 9% | 41% | 6% | Labour heartland held since 1935 falls; 24+ point swing to Reform |
| Newark | Mar 2026 | Con hold vs Reform | 18% | 35% | 32% | 6% | Conservatives held off Reform; Labour collapsed to third |
Reform UK Vote Share: By-Election Trajectory
What the By-Elections Tell Us About 2029
Reform UK wins at Runcorn (May 2025) and Blyth & Ashington (Jan 2026) confirmed the party can convert polling leads into Westminster seats. Both wins came in formerly safe Labour territory, demonstrating that the Red Wall - already cracked by the Conservatives in 2019 - is now fragmenting along a new Reform axis.
Labour's majority in Wigan was reduced to under 3 points in October 2025. Blyth & Ashington - which returned a Labour MP continuously since 1935 - is the starkest indicator yet. If these trends persist to 2029, Labour could lose 40-70 northern and Midlands seats currently considered part of its core base.
The Conservatives polled just 9% in Blyth & Ashington - their lowest ever in the constituency. Even Newark, a traditionally safe blue seat, saw Reform close to within three points. The ability to hold existing 121 seats at the 2029 General Election is now in serious question, particularly in northern marginals.
Despite polling at 35-41% in several by-elections, Reform UK's national vote share is concentrated unevenly across constituencies. Under First Past the Post, geographic efficiency of votes determines seat count. Reform's path to government still requires concentrating votes in winnable seats rather than running up majorities everywhere.
The 2029 projection from by-election data
Applying by-election swing patterns uniformly to a general election is dangerous - turnout is far higher in general elections and some voters return to their preferred party when stakes are national. However, if Reform UK's by-election vote shares (averaging 27% across all seven contests) were replicated nationally at 28-30% in 2029, models suggest the party could win 100-160 seats under FPTP - enough to deny Labour a majority and potentially form the official opposition. Labour's parliamentary majority is currently so large (410 seats) that even a 15-point national swing to Reform would leave them with a working majority, but the composition of Parliament would look radically different.
Featured By-Election Deep-Dives
Runcorn & Helsby
Reform UK's first ever Westminster by-election win. A 25+ point swing from Labour. The moment the political map changed.
Blyth & Ashington
The ultimate Red Wall fortress falls. Labour held this seat continuously since 1935. Reform's 41% makes it the most dramatic result since 2024.