Even the most ardent supporters doubt the party will breach the 5 per cent threshold, so it will once again throw everything at Epsom, where a Banks victory would mean electoral survival.
Act is in some ways well positioned. It has more money - more than $1 million - in the war chest than for previous campaigns, membership has swelled to more than 1000 under Dr Brash, and it has prominent new candidates in party president Chris Simmons, former president Catherine Isaac, and former Federated Farmers boss Don Nicolson.
It has also injected young faces David Seymour and Stephen Whittington, who it considers bright stars and potentially future leaders - if the party survives.
The top 12 on Act's list have been meeting every week as a shadow caucus, free from any baggage from this term's five departing MPs - though the unexpected retirement of John Boscawen is a huge loss.
Act is hoping Dr Brash's economic credentials as a former Reserve Bank Governor will resonate on the campaign trail. The message is to cut Government spending, peg future spending to inflation and population growth, sell state assets and expand mining.
Other key policies will be zero-tolerance on low-level crime, performance-pay for teachers, and cutting Working for Families for middle- and high-income families.
In the past Act has had a late 2 to 3 per cent surge in the polls, and it believes it can woo more voters on niche issues: scrapping the Maori seats, bringing back youth rates, and suspending the Emissions Trading Scheme, where Nicolson could swing farmers to Act.
Furthermore, John Key has not ruled out Dr Brash or Banks from future cabinet positions, showing that he still sees the parties as coalition bedfellows.
However, none of that will matter if Mr Banks doesn't win Epsom. Chances are that Mr Key and Mr Banks will share a coffee in front of media in the last week of the campaign. But Mr Key will also be wary that voters don't always appreciate such tactics.
Banks is trailing National candidate Paul Goldsmith in some polls, and no one doubts that the fate of Epsom largely rests in the hands of Mr Key. If he wanted it to be National's, Act would be gone.
The record
* 2008 - 3.65 per cent: Rodney Hide retains Epsom and brings in four other MPs. Act signs a confidence and supply agreement with National
* 2005 - 1.51 per cent: Against predictions, new leader Rodney Hide wins the seat of Epsom and brings Heather Roy into Parliament.
* 2002 - 7.14 per cent: Act wins 9 seats again, no electorate seats
* 1999 - 7.04 per cent: Act wins 9 seats, although leader Richard Prebble loses Wellington Central
* 1996 - 6.1 per cent: The party has 8 MPs; leader Richard Prebble wins Wellington Central after a tacit endorsement from National PM Jim Bolger
In their own words: Don Brash
* On the most important task for the party: "To increase the party vote to reflect the fact that a significant number of New Zealanders - about 25 per cent in fact, in market research we have commissioned - would like to see Act as a part of the next Government ... Act is the most logical coalition partner for National."
* On how he has gone since taking over the leadership: " I've made some mistakes, and I've learnt from those mistakes [referring to his public support of decriminalising cannabis]."
* On whether Act is still damaged goods: "The brand was damaged, but I think we have substantially changed that perception. The leader has changed and we have a strong line-up of candidates on the list, as good as any party. The people who caused the perception of damage to the brand have, without exception, gone."
* On his relationship with National and John Key: "It was I who appointed John Key to be finance spokesman for the National Party, and I strongly endorsed him as my successor as National leader. I don't doubt at all that we can work constructively."
* On the perception he and Banks are too old and National's hand-me-downs: "Some of the most distinguished politicians in the world are older than I am. And no (Banks and I are not National's men) but we've been quite explicit that we would support a National-led Government. If you want a John Key-led Government which will deal with issues that have not been dealt with effectively in the last three years, you should give your party vote to Act."
