Are the Greens and Reform Replacing Labour and the Conservatives?

TL;DR

Reform and the Greens are genuinely threatening Labour and the Conservatives, but a full two-party replacement still looks distant.

Key Points

• 1.Gorton and Denton by-election: Greens won with 40.7%, Reform second at 28.7% — the first postwar English Westminster by-election where neither Labour nor the Conservatives finished in the top two. The Tories lost their deposit.
• 2.Polling collapse: Labour is now polling ~15 points below their 2024 result (as low as 16% in one YouGov poll), while Reform is 14 points higher and the Greens are 8 points higher than their election results.
• 3.Duverger's Law pressure: The UK's first-past-the-post system should suppress smaller parties via vote-splitting fears, but 91% of Reform considerers don't cite "wasted vote" as a concern, suggesting Reform may already be crossing the tipping point into mainstream status.
• 4.Greens face a ceiling: Despite the Gorton win, national polling aggregators still show Labour trailing the Greens by only a few points, with Labour appearing to have bottomed out — and the Green result was boosted by a strong local candidate and Labour blocking popular Andy Burnham from standing.
• 5.Five-party future: Rather than a straight swap of faces in a two-party system, the UK is trending toward a Dutch-style five-plus party fragmentation — which, combined with first-past-the-post voting, could produce highly unpredictable election results.