Last week, a Herald-Digipoll survey showed support for the Greens at 12.6 per cent. This was heady stuff for a party that had polled below 10 per cent for most of the past decade. The Greens were being talked about as possibly being a pivotal factor in post-election negotiations. Now, however, they will be eyeing forthcoming polls with some trepidation. A party member's co-ordination of the defacing of hundreds of National Party billboards has echoes of some of the Greens' more extreme protests. It may be enough to make some of their new-found supporters think again.
There was nothing particularly heinous about the attack. Billboards are routinely vandalised during election campaigns. In this instance, about 700 belonging to National were altered by activists, who fixed subversive slogans, such as "the rich deserve more".
But this assault was organised by a member of a party that has always prided itself on conducting clean campaigns. In one swoop, Jolyon White's link to the Greens sank them to the depths of other parties.
To make matters worse, he is the partner of the executive assistant of the Green co-leader Russel Norman. She had not told Dr Norman of the planned action, which involved about 50 people, some of whom must surely have been Green Party members. This led the Greens to initially deny responsibility for defacing the billboards.
When the facts emerged, Dr Norman, unsurprisingly, pronounced himself "incredibly disappointed". He said that he did not know about the attack. There seems little reason to doubt that. It went against all that he has tried to achieve, not least in enhancing the party's appeal to middle-of-the-road voters who had previously considered some of the Greens' policies too radical.
Its economic policy and proposed improvements to KiwiSaver had confirmed a willingness to consign its image as a collection of tree-hugging environmentalists to the past. Now, an act of errant activism has reminded voters of that history.
Dr Norman has done as much as he could to limit the damage. An immediate apology to John Key on behalf of the Green Party and an offer of help to repair the billboards showed a willingness to confront the issue. As well, Dr Norman's assistant was stood down, and action was taken against Mr White, who resigned from the party after being told he faced an internal Greens inquiry.
Nonetheless, this was an embarrassing slip for a party seeking to become a serious force in politics.
The younger voters who are traditionally the party's mainstay may regard the episode as the product of nothing more serious than errant enthusiasm. But others, including many of the customary Labour voters who are contemplating supporting the Greens for the first time, may take a sterner view.
Dr Norman noted that of all political parties, the Greens were most acutely aware of the impact of such activities.
This was a reference to the initially anonymous leaflet attack on the party by the Exclusive Brethren in 2005. During the ensuing controversy, Don Brash, the National leader, got into bother after admitting he had known the Exclusive Brethren were responsible. Earlier, he had said that he had not known. The about-turn may have cost National the election.
Now, the Green Party co-leader has been blindsided, and by someone far more closely related to the party than a minor religious grouping.
Mr White's calculated attack was not only totally at odds with the Greens' pristine pronouncements but a reminder of an extremism that had previously consigned them to minor-player status. It also gave ammunition to other parties. Suddenly, the Greens' lot seems much less comfortable.