It is also one of only four National strongholds with a 25,000 party vote target for this election.
Act candidates have held the seat since 2005 and Mr Banks' former staffer David Seymour is hoping to continue the party's legacy this election despite his predecessor's ignominious departure.
Epsom has been without a sitting MP since June, when Mr Banks resigned from Parliament after being found guilty of filing a false electoral return.
Mr Seymour, whose introductory campaign video was mercilessly ridiculed on social media for its questionable production values, said he had been adamant "there will be no beverage-based gestures in 2014".
He said he had been campaigning fulltime since February and claims to have door-knocked more than 11,000 properties in the electorate.
The number one issue for the electorate's voters was that "local government had grown out of control", Mr Seymour said.
To his critics, Mr Seymour said: "You've got to remember St Francis of Assisi - give me the courage to change the things I can, serenity to see the changes I can't and the wisdom to know the difference.
"I can't change MMP, I can't change the mathematics of it, but what I can do is win Epsom, rejuvenate the Act Party and ensure that there's a centre-right coalition."
Mr Seymour's most vocal critic is Labour's Epsom candidate, Michael Wood, who said the people of Epsom did not deserve to be "treated like pawns on a chessboard" to prop up the Act Party.
But despite any distaste for the deal, polling suggests voters will go with it.
The most recent poll of Epsom voters - conducted by Colmar Brunton for TVNZ and released on August 10 - had National candidate Paul Goldsmith at 44 per cent, trailed by Mr Seymour at 32 per cent.
But when voters took into account the deal with Act, Mr Seymour's support leaped to 45 per cent and Mr Goldsmith's dropped to 31 per cent.
The same poll showed 47 per cent of voters supported the deal.
A latecomer to the Epsom campaign was the Conservative Party's candidate, former Work and Income boss Christine Rankin.
Ms Rankin said she was considering standing in Upper Harbour, but a battle with pneumonia delayed her bid and she was excited by the challenge of standing in a bellwether seat.
Ms Rankin said her time door-knocking and canvassing in Epsom made it clear voters wanted a stable, centre-right government, but were angry about being told "what to do and who to vote for".
Ms Rankin described herself as a "fiercely determined woman" and claimed that on current polling she would take three to four MPs into Parliament with her if she won the seat.
Mr Goldsmith has said that by remaining on the ballot for Epsom he gave voters who didn't want to vote for Act a choice, and his position on National's list - at number 30 which all but guaranteed his return to Parliament - meant he was well-placed to represent Epsom voters.
Green Party candidate Julie Anne Genter has been campaigning solely for the party vote as is the party policy.
The Greens are the second-highest polling party in the electorate and, at 16 per cent, are one percentage point above the party's national target and two points above Labour.
A proposed boundary change for Epsom was dropped this year after the Representation Commission's proposal to move the boundary further north, putting about 4400 Epsom voters into the Mt Roskill electorate held by Labour's Phil Goff, received about 700 objections.
The proposal raised fears that homes would be taken out of the Auckland Grammar zone and property values would be affected.
In its final decision, the commission instead trimmed Epsom by moving Auckland Central's boundaries to include part of Grafton and Newmarket. APNZ
