So it is done; a second successful by-election for UKIP. The headlines will focus on the blow to the Conservatives, and it is a big blow, but the result is also important for the left.

Labour secured only 16.8% of the vote in a seat they held before 2010. These are the seats they need to win back if they want to govern after May. Much worse was the Lib Dem* result, with 0.9% of the vote. The Greens, however, are on the rise, and performed well, receiving 4.2% of the vote. The winds of change are blowing on the left of politics as fiercely as on the right.

Business gurus often talk about ‘disruptive innovations’ developing new markets as they make old markets obsolete. UKIP is a disruptor. Their innovation has been to reframe the political debate. It’s not just about right and left now, it’s about politics and anti-politics. As with most disruptive innovations, there is more than one beneficiary. On the left, it is the Greens.

The Greens have quietly ridden a left-leaning anti-politics wave. Often, those who say they intend to vote Green don’t actually know their policies but they know they are left-wing and concerned by climate change and social justice. They also know they aren’t one of the parties who’ve been disappointing them throughout their lives. This is enough for some voters. They feel disenfranchised by Labour and the Conservatives. They no longer trust the centrist Liberal Democrats. So they lodge their protest vote with the Greens.

However, this analysis is somewhat disingenuous. The Greens, like UKIP, are not just a protest vote.  YouGov polling published on 20 November showed that if people thought they could win, 26% of people would vote for the Greens, putting them in third behind Labour and the Conservatives, both on 35%. The same poll puts UKIP fourth (24%) and the Liberal Democrats in fifth (16%). This suggests voters believe in them. Climate change is the great challenge of our time, and it would be fair to say that Labour and the Tories don’t give this a lot of focus. The Liberal Democrats do but it is not the founding principle of the party; it is for the Greens.

For the Lib Dems, the Greens are a very real threat. They aren’t for Labour, but they’ll take votes off them in a tight election where they need all the votes they can get. So what is the key battleground? Polling indicates that younger voters trend left, with some exceptions. With 18-24 year olds, the Greens are polling at 18%, three times their national average (6%); the Liberal Democrats poll in line with theirs (7%); and Labour is polling below its average (33%) with 31%. The trends for 25-39 year olds are closer to national averages, though 40% of this group support Labour, 9% the Greens and 8% the Lib Dems.This suggests that many young, left-wing voters now support the Greens where they would previously have supported Labour and the Lib Dems.

The Lib Dems have struggled because a u-turn on tuition fees pushed away a traditionally supportive student demographic and coalition with the Conservatives has alienated the left-wing.

This is not the case for Labour. Labour is likely to continue in its current form and remain united. Nonetheless, their chances of electoral success could dwindle as centrists depart the party and the Greens grow in support. Some polling in Rochester suggested Labour voters were supporting UKIP in a bid to embarrass the Tories. This would seem a logical explanation for Labour’s collapse in support in the constituency, having secured 28.5% of the vote in 2010. However, given UKIP’s near-win in Heywood and Middleton in October, where they almost overturned a Labour majority of 5,971 to lose by only 617 votes, we shouldn’t take such a simple view. Working class voters are a key demographic for Labour and they are increasingly attracted to UKIP, whose right-wing policies make it difficult for Labour to respond.

Emily Thornberry’s tweet, while campaigning in Rochester, of a white van parked outside of a house hanging St George flags that she found a novelty, only reinforced a view that Labour is part of a ‘Westminster elite’. This perception is draining support in Scotland but could also come into play in the North of England, where UKIP is making gains.

This by-election and the other elections that have taken place since 2010 indicate where votes may go in May. However, the question asked in these elections seems to be “how happy are you with the current government?”, rather than the question voters will answer in May, “who should lead this country?” Nonetheless, there’s been a shift on the left; that much is clear.

It’s uncertain if Labour can win the election. The Lib Dems are in a fight for survival. The Greens? They’ll struggle to win many seats in 2015, but they’ll continue to be a disruptive influence, splitting the left’s vote and establishing themselves in the new multi-party landscape.

*Although a centrist party, the Liberal Democrats have traditionally benefited at the ballot box from strong left-wing support.

**YouGov/Sun polls published on 20th November.