The theory that the recent surge in Green support has primarily been driven by disillusionment with Kevin Rudd rather than the appeal of the Greens has been backed by new research from Essential Research showing the Green vote is much softer than that of the major parties.

Essential regularly asks voters about firmness of voting intention and there have been significant trends in recent months.

The Coalition has significantly firmed up its level of support since early March. Back then, it had a slightly higher level of strong support and about the same level of middling and weak support in its vote as Labor.

Not longer after, the Liberals picked up a 3-4 point rise in its primary vote from Labor that they have kept ever since. But that has been coupled with a big rise in ‘very firm’ support — from 52% to 65%. ‘Might change’ votes fell 7% and there was a drop in ‘soft’ support from 16% to 10%.

So not merely have the Liberals picked up votes, but their new supporters and/or existing supporters are stronger in their voting intention — just what you want heading toward an election.

At the same time, Labor has shed votes, mainly to the Greens, but has strengthened its firmness of support. ‘Very firm’ votes have increased from 48% to 51% and ‘soft’ votes have fallen from 16% to 11% — almost as much as the Liberals.

Given Labor has been losing votes to the Greens and the Liberals, this makes sense — the voters most likely to shift have gone and shifted, leaving behind stronger voters.

And the voters that have shifted to the Greens are uncertain as to how they really will vote. Green ‘very firm’ votes have fallen 10% to 31%, ‘might change’ has gone up from 39% to 45% and ‘soft’ votes have gone from 18% to 22%.

Again, assuming these are Labor voters driven leftward by the government’s CPRS decision, the relative softness of the Greens vote makes sense. These are voters who could yet be wooed back by Labor — or lured by the Liberals, if they can find a way.

A complicating factor, however, is that Essential’s data shows voting intention becomes firmer with age (perhaps one of the few things to do so). Only 35% of 18-24 voters have ‘very firm’ voting intentions. It steadily increases with age from there, right up to 63% of people over 65 saying they have ‘very firm’ voting intentions. Voting softness also falls in exactly symmetrical fashion. Only 11% of retired voters say their vote is ‘soft’ compared to nearly a quarter of young people.

This necessarily strengthens the Coalition vote since the Liberals and Nationals skew old, and tend to perform most strongly amongst people over 65.

If the Greens can’t convert this soft support into actual votes come the election, they’ll have to regard 2010 as a huge missed opportunity. Voters were prepared to consider switching to them in large numbers, but they were unable to keep them from drifting back to Labor or, possibly, the Liberals.

As for the Opposition, they’ve been doing everything right — but where to get that extra 2-3% of primary vote that would get them ahead of Labor in two-party preferred terms? With Labor’s vote firmer due the loss of defectors, it makes more sense to target the soft Green votes, but it’s hard to see Tony Abbott managing that.