At long last the media is covering the Green Party. While calling it a surge may be a little premature, today's poll showing them on 8% (once again above the Liberal Democrats) is highly newsworthy. As someone very much on the left of British politics I consider this a cause for celebration. The Greens are achieving the recent period of success not by clinging to the centre ground or by focussing purely on environmental issues. On the contrary it is their promotion of an explicitly left wing and anti-austerity agenda that has brought their recent success, as they have been able to stake out ground vacated by the unceasing neo-liberalism of the other parties (including UKIP). There has long been a need for a populist but credible party to the left of Labour - throughout the Blair and Brown years, New Labour wooed centre right voters in the knowledge that the party had no competition on its left flank. Just as UKIP has forced the Conservatives to pay attention to its core voters the Greens are showing Labour that what it views as it's traditional vote can no longer be taken for granted.
Ironically this has come at a time when, in Ed Miliband Labour has the most leftwing leader it has had in 20 years: policies like rent controls, energy price freeze and increasing taxes on the richest more would have been unthinkable under Blair or Brown. It may well be that Labour's move to the left (however timid) has opened us space for the Greens - the Labour leadership's tame opposition to austerity has laid the grounds for the more full blooded one coming from Natalie Bennet and Caroline Lucas.
But the fact that the vast majority of Green voters would otherwise vote Labour also causes problems. Labour have polled above 35% for most of the last 4 years - but in recent months they have sunk to the low 30s. So while for most of this Parliament the working assumption has been that Labour could win a modest majority in 2015, a surge of Labour voters moving to the Greens could instead result in Cameron remaining Prime Minister, either as head of a Tory Minority government or in coalition with the remaining Liberal Democrat rump.
If we had a system of proportional representation we wouldn't have this problem - the two parties could fight each other during the election and then work together as natural coalition partners -holding approximately 40% of the seats in Parliament between them. But of course we don't have proportional representation - we have our archaic first past the post system in which small parties gain few or no seats even if they gain up to 10% of the vote. In our existing political setup, leftwing voters opting for the Greens risk allowing Cameron's government - with its viscous austerity programme - a second term.
On the other hand there is something uncomfortably familiar here - Labour voters are forever hearing that voting for someone other then Labour will let the Tories in. It may be true, but with that approach we will never build a genuinely left wing party and British voters will stuck with the unappealing choice of right or further right. So simply telling Green-inclined voters to stick with Labour to kick the Tories out is insufficient (and likely to fail). Instead the left needs to be a little less high minded and a lot more tactical.
There are some seats where voting Green is sensible and others where it is deeply unwise. Brighton Pavilion is the number one place to vote Green. Caroline Lucas has done a sterling job as Britain's first Green MP - and has a decent chance of holding the seat. Beyond this we should look to the Green's target seats of which there are another 11 - top of the list are Lib Dem held Bristol West and Norwich South, where the Greens have substantial support. This is exactly the right tactic - the only way small parties can win under First Past the Post is by targeting a handful of constituencies - as the Lib Dems did in the 1990s and UKIP are doing now. So these 3 seats represent the best places to vote Green. In addition there are many seats that are either so strongly Tory that voting Labour is not going to help or so strongly Labour that a substantial Green vote is not join to change the result. Voting for Natalie Bennet's party here will have the effect of boosting the nationwide Green vote without risking giving seats to the Tories. It would however be supremely un-tactical to vote Green in marginal seats where Labour are defending a narrow lead or trying to overturn a small Conservative or Lib Dem majority, and where the Greens are nowhere near strong enough to win. A strong Green vote here could easily mean a Tory or Tory-friendly Lib Dem being elected, and is thus totally counterproductive.
This approach may not seem very principled - and may also seem rather demanding as it demands voters spend time on sites like UK Polling Report and peruse local polling in order to ascertain the relative strength of the parties in their constituency. But this is what voting under first past the post requires - if we want to build a genuine progressive politics in this country there is simply no alternative.