Time for the Lib Dems and Greens to do deal?
Could the Greens do to the Liberal Democrats what UKIP is threatening to do to the Conservatives at next year's general election?
It has already happened, in this year's elections for the European Parliament. The Greens out-polled the Liberal Democrats. In the south-west of England, people elected a Green MEP instead of a Lib Dem.
Andrew George has been the MP for St Ives in Cornwall since 1997. His majority at the last general election was 1,719. The Greens took 1,308 votes.
Since then, we've had the European elections, with the Greens taking 16,000 votes across Cornwall. Given their poll rating touched 6 per cent this week (YouGov/The Sunday Times), it's not surprising that Andrew George thinks his party should consider a "pact or arrangement".
This is not the nationwide deal that Jacob Rees-Mogg MP has proposed between the Conservatives and UKIP. Mr George reminded me that local arrangements in Tatton in 1997 and twice in Kidderminster, in 2001 and 2005, resulted in the Lib Dems not running candidates.
He clearly hopes that if Brighton Lib Dems don't stand against the solitary Green MP Caroline Lucas, the Greens might reciprocate in seats like his.
That rests on two assumptions. First, that the surge in Green support is coming from disaffected Liberal Democrats. Peter Kellner, president of YouGov, says there's clear evidence of that: "They're taking votes from the Lib Dems far more than anywhere else."
Second, that the Greens are willing to negotiate.
My conversation with Caroline Lucas suggests not.
"For as long as that MP is part of a party," she told me, "which is going in exactly the wrong direction on everything from fracking, nuclear power, and nuclear weapons, then I don't think that's got much traction."
Frustrated by the effects of the first-past-the-post voting system, the Liberal Democrats used to argue there should be room for more parties. Now Greens and UKIP are the parties of insurgency, accusing Lib Dems of being part of a system that needs to change.
If the outcome of the next general election is no Green MPs, and green-tinged Lib Dems losing their seats - to what Andrew George derisively refers to as "grey" Tories - both parties might regret not matching their talk of a more plural politics with action.