Being excluded from the TV debates has been the best thing that could possibly happen to the Greens, it seems. Already over 100,000 people have signed a petition calling for the party to be included, and their membership in England reached 21,000 this week. Natalie Bennett and Caroline Lucas have enjoyed more media exposure than they have done for a good long while. The idea that the Establishment is trying to silence the Greens is also really helpful for their insurgent party credentials, as nothing enthuses supporters more than the sense that they are pushing against a Westminster conspiracy.
But in spite of having an MP in the House of Commons - while Ukip, which is invited to the TV debates - didn't until last week, the Greens have long struggled to get the same level of media exposure as Nigel Farage's party. This is partly because while Natalie Bennett may or may not be very good at enthusing the growing party membership and organising the Greens to campaign, she lacks the enthusiasm and charisma that Nigel Farage and Alex Salmond both possess. Her outsider status should be helpful in an era of anti-politics, but in terms of the national discourse, the Greens struggle to break through.
This means that the main parties may have been more complacent about the threat of the Greens than they are about the threat of Ukip. They are very rarely asked about the former, yet the latter looms large in every interview. But the Greens are still chipping away at the leftwing vote, possibly splitting it in a similar fashion to the way Ukip threatens Tory seats by creating two right-wing options.
Labour last month set up a Green attack unit in its headquarters, led by Sadiq Khan. The group, which includes party staffers and Khan's advisers, will create a toolkit of local campaign materials for constituencies to use and advise on a national media strategy to combat the Greens.
It will be interesting to see what this media strategy ends up looking like. If Labour is to combat Ukip, which is causing its MPs in the North serious jitters, then it will struggle to also communicate with the Greens. This appears to have been its problem in Heywood and Middleton: you can't pitch both for ex-Lib Dem voters and for Ukip voters without either sounding a tad confused or giving both groups of voters the impression that you don't mean what you're saying.
One of the ways in which the Greens have attracted votes from Labour is by pitching themselves not just as a tree-huggy environmentalist party but as the only anti-austerity party with a sufficiently loud voice in the political debate. Whenever Rachel Reeves makes a tough speech on welfare designed to appeal to the voters who thought Labour had gone soft on benefits, Natalie Bennett is often first out of the blocks to criticise the policy. Labour knows it must talk tough to the wider electorate, but as it does this, the Greens are trying to chip away at its core.
One party thinker points out that the post-mortem Labour is now starting to hold on the result of the Scottish referendum, which saw Labour areas back 'Yes', should also consider that the Scottish Greens appear to be very close to having a similar number of members to Scottish Labour.
The Lib Dems haven't run focus groups with ex-Lib Dem voters who have gone to the Greens, while they have done so with Ukip voters. I understand that the party also neglected to discuss the Greens during their training sessions with candidates, activists and MPs at their conference earlier this month. But they are aware of seats where the Green party poses significant risks to their vote, including Bristol West and Solihull. They recognise that as a largely metropolitan liberal vote, Greenish voters are just the sort they're aiming after themselves (Ian Warren's analysis of who Green voters are and where the party could do well is essential reading on this)
The party's strategy is largely to highlight those things that appeal to Greens, including blocking the Communications Data Bill, the Pupil Premium, pension reforms, fighting child detention and female genital mutilation. They are particularly happy for Theresa May to pick fights with them over the Comms Data legislation as this enables them to make vocal appeals to would-be Greens about their civil libertarian stance.
But there is disquiet in some parts of the country where the Greens pose far more of a threat than Ukip. Where Nigel Farage's party did poorly, the Greens flourished, and in doing so created serious problems for Lib Dems. Party figures who worked on the local elections in London have written to the national party to complain that they felt under 'Green siege' and were not given any narratives and arguments by the national party to counter it. They reported a direct correlation between the Lib Dem vote falling and the Green vote going up, leaving councillors who'd held seats for many years in fourth place.
One source in the London Lib Dems tells me that the Green 'siege' this May was not anticipated by the party:
'As a party of government, there was an element of this which was inevitable, and the British do like an underdog and to give the establishment (which we have now become) a bloody nose. But no thought or direction was provided from the centre as to how to counter this, indeed, it was not anticipated due to the weakness of our central London campaigns team.'
The Greens are creeping up on the left-ish parties, just as Ukip crept up on the Tories. Everyone is more aware of the threat insurgent parties pose to mainstream politics, but this party is still largely dismissed as a bit boring. But when a party's General Election strategy involves it leaning on its core, it's wise to make sure that the core is safe to lean on, rather than quietly rotting away. Keeping an eye on those Greens, who may be boring away at the core even as they appear boring to the broadcasters, would be a small but smart move.