The Green Party has enjoyed a rise in support in recent years. In 2019, the Greens only secured 2.7% of the vote. In 2024, this rose to 6.7%. After Polanski’s leadership bid in May 2025, the party more than doubled its support, averaging 14% in the polls during the May 2026 local elections. This paper explores the increase in support for the radical left in Britain by examining the growth of the Green Party. 

To do this, it uses the British Election Study to identify which new voters supported the Greens in the previous parliament (2019 - 2024). It also analyses which voters have moved to them in the current parliament, which in 2026 led to their highest-ever poll ratings. In both periods, it explains the main factors that drove these voters to switch. 

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This paper's core argument is that the perceived rightward shift of Labour under Starmer and incompetence on core issues progressive voters value have weakened Labour support. The Greens have exploited these weaknesses and gained considerable support, a trend that has gathered pace after Polanski’s leadership bid. The paper also argues the Greens have gained progressive voters from other mainstream parties deemed to have failed on the core issue Green supporters tend to highly value.

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