What reasons did Zack Polanski give publicly for leaving the Liberal Democrats?

1. The immediate trigger: the Richmond Park selection dispute

Multiple biographies and summaries say Polanski put his name forward for the Richmond Park by‑election in December 2016, was not shortlisted, and that this episode directly fed his decision to leave the Liberal Democrats and join the Green Party in 2017 ^{[1] [2]}. Reporting and derived profiles link his exit to that local candidate selection — framed as the decisive, proximate cause ^{[1] [2]}.

2. His stated grievance: “not interested” in a gay Jewish renter’s contribution

A secondary account cited on his Wikipedia page quotes Private Eye saying Polanski felt the Lib Dems were "not interested in what he could contribute as a 'gay Jewish renter'." That phrasing appears in biographical summaries as his own reaction to the Richmond Park decision and is presented as a personal reason for leaving ^[1].

3. Broader political realignment: ideological fit and refugee policy

Contemporary profiles of Polanski point to a broader political shift rather than a single grievance. ITV’s profile notes he switched to the Greens in 2017 after hearing the party’s stance on refugee rights, implying policy alignment on humanitarian issues played a role alongside selection disputes ^[3]. BBC and Sky reporting similarly describe his move as part of a move leftwards because he now criticises the Lib Dems as insufficiently left‑wing ^{[4] [5]}.

4. How sources frame ambition versus principle

Some commentary suggests ambition and local opportunity informed the split: blog and local accounts argue Polanski had higher ambitions and that not being chosen for Richmond Park prompted his exit ^[6]. Other mainstream outlets emphasise principle — disagreement over policy and a closer fit with Green positions on refugees and climate ^{[3] [4]}. Both narratives appear in the available reporting ^{[6] [3] [4]}.

5. What Polanski emphasises today and how that retrofits the story

Recent interviews and profiles of Polanski as Green deputy and now leader show him casting his earlier Lib Dem membership as a stepping stone; he criticises the Lib Dems as “insufficiently left‑wing” and portrays his politics as better suited to Green eco‑populism and radical redistribution ^{[4] [5]}. These later statements offer a political rationale that supplements the immediate selection dispute reported at the time ^{[4] [5]}.

6. Limits of the record and competing accounts

Primary firsthand statements from Polanski at the time of his departure are not present in the supplied sources; what is reported relies on secondary accounts (Wikipedia citing Private Eye, profiles and retrospectives) ^{[1] [2]}. That means the most concrete contemporary claim in these sources is the Richmond Park selection dispute and the Private Eye‑attributed quote about feeling excluded; other sources add ideological reasons later on ^{[1] [3] [4]}.

7. Why this matters politically

The mix of personal grievance (selection processes and perceived exclusion) and political realignment (policy on refugees, climate, left‑right positioning) explains both why Polanski left and why his move resonated: it maps on to wider debates about candidate selection, inclusion of minority voices in party structures, and the appetite on the left for more radical platforms — themes emphasized across profiles ^{[1] [3] [4]}.

8. Bottom line for readers

Available sources consistently identify the Richmond Park non‑shortlisting as the proximate reason and quote a feeling of being unwelcome as a “gay Jewish renter” (via Private Eye), while later interviews and profiles add that policy alignment with the Greens — particularly on refugees and climate — and a shift further left politically also explain his switch ^{[1] [3] [4]}. Sources do not include a verbatim, contemporaneous statement from Polanski beyond what secondary outlets report; that absence shapes how confidently each motive can be attributed ^[1].