Here's one for those Tui signwriters: Election outcome swayed by billboards. All together now... Yeah Right. Untold effort and expense, if not creativity, goes into producing the myriad of party and candidate hoardings that spring up like unwanted weeds every election campaign, only to disappear on the eve of polling day.

Here's a thought for those who make their living devising and conducting opinion polls. How about a survey seeking to establish whether somewhere, anywhere, a single voter has been empty-headed enough to cast his or her votes based simply – or even partly – on the message contained on a political billboard?

Surely, motorists don't bother to gaze at the motley displays cluttering Nelson gateways such as at Atawhai's Miyazu Park or Bishopdale Hill? Those who do, risk being distracted from the task at hand and tailgating the vehicle in front. Political parties might see any such accidents as mere collateral damage, the price of democracy, but it is tempting to see these billboard forests as no better than inane insults to our intelligence, extreme visual pollution and therefore fair game for those who might seek to "improve" them with a splash of wit and humour.

The large-scale defacing of National Party billboards brought a curious twist, more comedic than nastily machiavellian, to a week dominated by the storm over the cup of tea in Epsom. The Greens are generally thought of as being way too politically correct to even know where the dirty tricks bag was, let alone dip into it. Though tracts of the party's support base have an activist bent, this has expressed itself more in stances on genetic modification or animal welfare than petty vandalism.

They once also had a reputation, among their detractors at least, for possessing heads so clouded with idealism that they could never be capable of a co-ordinated, covert, operation of this nature. Hitting 700 billboards over one evening almost sounds like a modern equivalent of a World War II sabotage raid, behind enemy lines. Besides, adding slogans like "The Rich Deserve More!" and "Drill it! Mine it! Sell it!" to the Nats' hoardings shows more ironic wit than your average earnest Green might be reasonably expected to possess.

The Greens did the right thing by the party they might yet end up in post-election relationship talks with following Saturday's general election, as galling as that might be to the hardliners of both parties. Raid co-ordinator Jolyon White is no longer a member, the Greens helped remove the offending stickers, and maintained hand-on-heart that word of the plan had not reached their upper echelon – even if Mr White's partner, Anne Heins, was co-leader Russel Norman's executive assistant and has since been stood down.

Grassroots members may wonder why Mr White and Ms Heins were not given the Green equivalent of a medal – a kawakawa garland perhaps – rather than being outed and ousted. However, the party has been adopting a more mature, professional line under Mr Norman and co-leader Metiria Turei. This is how the Greens have to play it if they are to enjoy a more significant role in the running of New Zealand – which, on current polling, looks certain.