Brash, who only took over as party leader from Rodney Hide in April, had said in an interview that Isaac was a "first class person", and "a potential future leader".
But Isaac told the Herald on Sunday: "I'm not seeking the leadership. I didn't become involved for that purpose."
Instead she wanted to foster young talent coming up through the party so it was in safe hands for the future. She said MPs David Seymour and Stephen Whittington would make great leaders.
Her fellow list candidate, Kath McCabe, also saw Seymour as a future leader and, with Brash now 71, it was inevitable that there would be a leadership change eventually.
But Seymour, number five on the list and a candidate for the Auckland Central seat, brushed off suggestions that he might fill Brash's shoes. He joked that he was a 28-year-old with a life expectancy of 82 and he might pitch for the leadership at some point in the next 54 years.
"I'm happy with Don. I like Don a lot." He said Brash was the only leader whose views fitted with the international consensus of good economic policy.
Seymour said the campaign had gone well and, thanks to Banks: "The Act Party dream stays alive." Seymour said the media had over-estimated the impact of the "teacup" tapes. On the campaign trail, people seemed to get back to the issues.
Act MP from 1996-2005 Richard Prebble said Act's messages "might have got obscured by cups of tea and the like".
"I would have thought that John Banks could have fought the election campaign on the basis of being a former mayor of Auckland.
"He's uniquely qualified to be an extremely good MP for the electorate."
He also said the leader could have better chosen his words when "musing" on the decriminalisation of marijuana because that and the "tea party fiasco" had really set the campaign back.
But a look back through the Act's history shows a party that's used to its policies being sidelined by its MPs' antics. Remember MP Donna Awatere Huata? She was the high-flying child literacy expert who had a makeover thanks to a secret stomach-stapling op and was later sent to prison for fraud.