It wasn’t so long ago that Zack Polanski was riding high politically, on the brink of making the Greens a truly nationwide party and with a huge personal brand. But it was long enough ago for none of that to matter now: he has failed to win the Holborn and St Pancras by-election, and in the eyes of many senior Greens, he has failed to lead the party responsibly. It is now in a mess that few seem to have faith in Polanski to be able to fix. 

Polanski was 3,000 votes behind Labour victor Sagal Abdi-Wali. He may well argue that his share of the vote increased a whole 22 points from the Greens’ 2024 general election result. But they weren’t fighting that seat in the same way, and he wasn’t the candidate. He had come under increasing pressure to stand for a parliamentary seat, and the constituency vacated by Keir Starmer, whose lack of passion and conviction had sent many voters to the Greens, seemed the perfect location. 

But Polanski wasn’t the perfect candidate – despite his initial success in charming people as Green leader. Neither are the Greens the party they could have been: like many single-issue parties, they’ve tripped over their attempts to focus on other issues. The SNP is another example of a party that would once force the words “Scottish independence” into a benign discussion, but which made the damaging decision to talk about something else.

The problem with single-issue parties is that even when they realise that voters aren’t currently preoccupied with the constitution or, in the case of the Greens, have been a bit freaked out by what net zero means for them, it’s hard to move to talking about run-of-the-mill issues. Instead, what tends to happen is that the party retains its myopia and merely turns to a different hot-button issue, but without the discipline that it had built up over its founding cause.

For the SNP, that manifested itself as a crusade on transgender rights that its own leading lights hadn’t really thought through. For the Greens, it was Gaza. Initially, the entryists who wrote the party’s “Zionism is racism” conference motion must have seemed pretty similar to other Greens: driven, angry about justice, keen to take a stand. Presumably, that’s why Polanski didn’t pay greater attention to the risks of allowing people who weren’t even Greens until recently to write an antisemitic motion which horrified his own colleagues and frightened British Jews. 

Now, Polanski has to work out how to take his party back to its principles. That doesn’t necessarily mean only talking about climate change, but it does mean booting out the members who’ve exploited its keenness to talk about Gaza. It also means changing the party’s structures so that such a motion could never be passed again. But it’s not clear whether Polanski has it in him to manage this. He couldn’t quite work out what he wanted to say about the motion even this morning as he reflected on his defeat, burbling that there were “parts [of the motion] I disagree with and parts I agree with”.

His predecessor Caroline Lucas certainly doesn’t seem to think he’s got it in him. In a interview after polls closed in Holborn and St Pancras, she said he hadn’t shown leadership on the motion, that it was a mistake for him not to have even voted on it and that “the jury is out” on whether he would be able to show the leadership to repair things. 

Had Polanski been standing in a different seat in the Starmer era, he might have been able to contrast his leadership with the weak prime minister. Instead, Andy Burnham is still enjoying a bounce and has managed to get his party talking about the issues voters are worried about, while also changing its policy on Israel. Polanski now has nowhere to hide, certainly not within his own party.