Last week Christine Milne was tossed on the political compost heap as Richard Di Natale assumed leadership of the Greens.

At first glance he seems to be a decent, sensible, former GP with environmental apprehensions, humanist inclinations and a potentially unusual dose of pragmatism relative to others in his party. His early suggestion is that the Greens could become a more mainstream force under his leadership — but can they?

The Greens are essentially a party of protest. Sure, that protest is themed around matters environmental, but qualitative and quantitative studies I’ve seen through years of political campaigning consistently show that rather than supporting policies of leafy loveliness, nearly 80% of Green supporters use their vote to tell major parties to get rooted.

There has always been a place for parties that thrive by virtue of not being someone else — you can’t spit in the Senate without hitting one of them. But the flipside of reaping dissent is that its faddish lifecycles tend to be short, because its delivery vehicles are largely interchangeable.

The Democrats shot to prominence with the proposition that they would “keep the bastards honest”, but once in power their behaviour slowly morphed into conventional bastardry.  They lost inspirational leadership and dithered to electoral insignificance.

Current acceptance of the Greens as a mechanism by which the Coalition and Labor can be punished is both their paramount strength and weakness. Glib posturing harvests easy votes but simultaneously caps the ballot from those who look for more.

My guess is that the non-mainstream protest vote hovers around 25%, so even if you are market leader in that segment, you still peak at perhaps 15% of votes. That means Greens can only be a side dish, not a main course.

If they are serious about becoming a third political alternative they need fundamental transformation.

To move to the mainstream, meaning to attempt to become a statistically credible third force in politics, the Greens must become pragmatists rather than poseurs.

“Politics,” Otto von Bismarck said,” is the art of the possible”. He later added: “Laws are like sausages, it is better not to see them being made.”

Major parties need to make pragmatic decisions, and they invariably involve ugly compromises. Horse trading the lesser of two evils, the greater of two rights and the smaller of two indignities is the ghastly grind of exercising political power.

The Greens often opt for overt political purity, but it can lead to unintended consequences. A recent example has been their rejection of the petrol excise levy, presumably based on their hatred and mistrust of all things Abbott. The end result? Greater use of fossil fuel.

Mainstreaming would mean that wallowing in conspicuous compassion would need to stop, and strategies would have to address what can be done, rather than grandstanding about what should not.

Practical policies would be a similar requirement. For example, their batty idea of having no airport in Sydney may thrill Green left readers and attract the Kombi-Van-and-sandals vote, but would turn them into a punching bag for travellers, render them anathema to business and be unlikely to be sufficiently embraced by the broader community whose votes they would need.

What should their stance be on the coal industry?  Shutting it and throwing its 50,000 direct and 200,000 indirect employees out of work won’t win mainstream hearts and minds. Have they a credible transition plan for a $60 billion industry that generates 41% of the energy we use, or are they locked in the “coal or death” dramatics of Milne? How would that fit within believable economic policy?

Would a mainstream party still intend to pull out of the ANZUS treaty? Would they continue to call for massive tax hikes for high income earners and companies, slaughter the private health rebate, abolish secret ballots before industrial action, nationalise “natural monopolies”, encourage non-competitive sport and advocate a death tax?

Good luck with that.

The scale of shift and compromise is easy to see in asylum seeker policy. Like it or not, demand to live in Australia greatly exceeds what the majority deem acceptable supply; in fact, gross global appetite is greater than our current population.

Preventing uncontrolled entry has tragically been proven to need blatant nastiness, or too many attempt to get in and hundreds die while doing so.

How would mainstream Greens wrestle with this conundrum?

Could they cope with being misunderstood by decent voters who are disengaged from the painful arithmetic of caps and effective deterrents, or would they revert to their intransigent, indulgent but solution-free posturing that facilitated dozens more deaths at sea?

Finally jettisoning the pixie dust and Kumbaya of soft-headed senators would be imperative. The cost of such shifts would be the collapse of the core Green protest vote, because another contender would capture disaffected complainants.

Would new voters more than offset this? Of course not; the competition is too fierce.

Perhaps the real question the Greens should address is not necessarily if they can realistically become a party garnering similar levels of support to Labor or the Coalition, but rather what genuine success looks like.

Control isn’t everything; there is an important role that can be played by minor parties in broadening, civilising and ripening debate, rather than blackmailing and posturing. Might they become the party that enables same-sex marriage, that finally initiates mature conversation rather than binary partisanship about the environment, or moves asylum seeker policy beyond the current orgy of overt unkindness?

Their hearts may be there, but do they have the chutzpah to make a difference rather than a noise?

Maybe that’s where the answer lies. To move to the mainstream the Greens must be willing to throw away their sanctimony, their senators and their supporters.

They won’t.

*Toby Ralph is a marketing, strategy and communications consultant who, among other things, has worked on nearly 50 elections across three continents. His book, Bullets, ballots and Kabulshit: an Afghan Election, is published by Penguin. He is a regular on Gruen Planet.