With Reform UK polling at 25–30% in early 2026, the question of seat conversion is critical. FPTP punishes parties with nationally spread but locally shallow support. Reform typically polls at 20–30% in most constituencies but rarely gets close enough to actually win.
Consider a simplified example. Imagine 10 constituencies, each with three parties polling 33-30-27. The party at 33% wins all 10 seats with 100% of seats despite only 33% of votes. The 30% party and 27% party win nothing. This is FPTP in its most extreme form, but it captures the dynamics at play.
For Reform to win seats in proportion to their vote, they would need to either:
A safe seat is a constituency where one party’s majority is so large that it would require an extraordinary swing to change hands. Traditionally, seats with a majority over 15,000 votes or 20+ percentage points are considered safe. There are roughly 200–250 safe seats in the UK.
Safe seats have several effects on politics:
The 2024 election created new safe Labour seats. Some that were marginal now have majorities of 15,000+. These will revert to competitive marginals in 2029 if current polling holds.
Marginal seats are those where two or more parties are closely matched. A conventional definition is seats with a majority of under 5,000 votes or under 10 percentage points. There are typically 80–120 genuinely marginal seats at any given election.
General elections are largely decided in marginals. A uniform national swing of 5 points to the Conservatives would flip perhaps 60–80 Labour-held marginals, potentially giving the Conservatives a majority even if Labour still leads in vote share nationally.
Our constituencies tracker shows current marginality estimates based on polling.
Most democracies use some form of Proportional Representation (PR), where seats are allocated broadly in proportion to votes. The main PR variants include:
Scotland uses the Additional Member System (a form of MMP) for Holyrood elections, which produces much more proportional results than Westminster. The 2021 Scottish Parliament election saw the SNP win 48% of seats on 48% of the vote — in sharp contrast to Westminster FPTP outcomes.
FPTP is the UK voting system where 650 constituencies each elect one MP. The candidate with the most votes wins. The party winning the most seats forms the government.
FPTP rewards geographic concentration. Extra votes above a winning margin in any seat are wasted. A party with 30% spread evenly nationally can win far fewer seats than one with 20% concentrated in winnable seats.
A safe seat is a constituency with such a large majority that it is very unlikely to change hands. Roughly 200-250 UK seats are considered safe. Votes for non-incumbent parties here are largely wasted under FPTP.
A marginal seat is closely contested between two or more parties. There are typically 80-120 genuine marginals at any election. These are where campaigns are concentrated and where elections are decided.
Under PR, parties win seats broadly in proportion to their vote share. Germany uses MMP, the Netherlands uses list PR, and Ireland uses STV. Scotland uses a hybrid system for Holyrood that is more proportional than Westminster FPTP.