A horse, so the saying goes, can be led to water. But there is no way it can be made to drink it, especially if it believes that water to be tainted. Such seems to be the case with voters in the Epsom electorate, who appear ready to deliver their own scathing commentary on the limits of political manipulation.
The National Party had intended Act would have a clear run in the seat by selecting a candidate who would concentrate on boosting the party vote.
In theory, this should have provided Act with a reprise of the result that has been its political lifeline since 2005. The voters of Epsom, however, seem disinclined to be so charitable.
Both a Herald on Sunday-Key Research poll of 500 Epsom voters and leaked internal National polls show National's candidate, Paul Goldsmith, has a solid lead. In the Herald On Sunday poll, 32.9 per cent said they would vote for him, against 18.9 per cent for Act's John Banks.
The sentiment in the electorate was further evident when it came to party allegiance. Of those polled, 67.6 per cent said they would vote National, while only 5.7 per cent favoured Act.
Several factors underpin the reluctance of the many National voters in Epsom to again split their vote strategically, giving their candidate vote to Mr Banks.
The first relates to the way in which Act has besmirched its reputation over the past three years through infighting and self-inflicted blunders.
The upshot of this turmoil is that none of the five MPs elected to Parliament in 2008 will return.
In their place would be Mr Banks, the new party leader, Don Brash, and anyone else dragged in on Act's nationwide vote.
That prospect also appears to hold little appeal. Rodney Hide, the Epsom MP and Act leader deposed by Dr Brash, at least brought a sense of novelty and vitality. Mr Banks is a man seeking a third life in politics.
His lot, if elected, would surely be to languish in the halls of Parliament, rather like Sir Roger Douglas in the just-completed term.
The voters of Epsom are delivering a similar verdict on Dr Brash, another former National MP. When he claimed control of Act, it was expected that he would return the party to its founding principles and trigger a regrowth of its support base.
This has not happened. Indeed, Dr Brash has created confusion among potential voters by straying into areas such as cannabis reform.
His backing for softer drug laws was hardly likely to find favour in a conservative seat such as Epsom, and has served only to engender disharmony between himself and Mr Banks.
It could also be that many voters in the electorate believe National no longer requires Act to keep it in office. Polls indicate that National may win enough votes to govern alone.
If so, the last reason to vote Act disappears. But historically, the gap between National and Labour tightens as polling day approaches. If that happens this year, National will require coalition partners.
This probably explains why the Herald on Sunday-Key Research poll showed 41.5 per cent of those surveyed had not decided how they would vote.
With more than six weeks to polling day, these people doubtless want to get a clearer picture of the lie of the land.
They would like to have a better idea of whether the best outcome for National would again result from them voting strategically.
Clearly, however, many National supporters have made up their minds.
They have decided Act is beyond the pale whatever the entreaties of National's leadership, and that it has no place in Parliament. Paradoxically, all that is likely to change their mind, and persuade the undecided to vote for Mr Banks, will be an unexpectedly strong Labour showing on the hustings.