If green issues are interesting more voters, then why isn't the Green Party doing better?
Their share of the vote only registers in polling data under the rather dismissive heading "others".
One explanation is that hobbles itself with its determination to be different to the other parties - in particular by not having just one leader but two principal speakers.
The party is going to ballot its membership in the autumn over whether to replace that with a single leader.
This may sound like mere naval gazing, but for both sides it's an issue which goes to the heart of what kind of party the Greens want to be.
Earlier Elinor Goodman spoke to the MEP, Caroline Lucas from the Yes campaign and Derek Wall. who is one of the two principal speakers and fears going over to a single leader would undermine the party's basic philosophy.