Morgan, completely straight-faced, told reporters he expected the party to get 10 per cent on election day.
Still unsmiling, he said he expected to get 30 per cent in 2020, before breaking out into a grin: "I always like a challenge."
Asked where those votes would come from, Morgan said TOP would "skim the cream" from a few parties and would "pick up a few" from the Greens.
"They may well bounce back, but I think if they're going to lose they'll lose some to Labour and some to us."
He admitted that despite securing 4000 paid-up members, TOP's main barrier to election was getting noticed above the better-funded, old parties. It was depending largely on the "viral spread" of its policies online.
Asked who was voting for him, Morgan said his supporters were not just youngsters drawn to ideas like a basic income of $200 a week. Many of them were parents or grandparents who had generational concerns, like their kids getting locked out of the property market or facing the uncertainty of a more casualised workforce.
That was the key message in his speech - that New Zealand was once a place which prided itself on a "fair deal" and ensured that each generation was better off than the last.
"Something has gone terribly wrong with that idea," he said.
"The current generation, the baby boomers, may be the first to leave behind a New Zealand of shrinking opportunities, less fairness and more inequality than they were born into."
Rising inequality would not be solved by "more of the same old, same old" and needed radical change, like his party's plans to overhaul the tax system and replace welfare and the pension with a basic income.
His party had the advantage of being "free of the hatred of old tribal politics", he said, and could work with any political party.
Asked later which party he was leaning towards if TOP got into Parliament, Morgan said whichever one agreed to adopt the most TOP policies.
"I will just say we've got 15 policies, how many are we allowed to do in the first three years?"
At the end of his speech, the crowd broke into a chant of the party's slogan: "Care, Think, Vote." The candidates, who were gathering as a group for the first time, posed for photographs.
The small audience at the event was mostly white, older, and educated, and there were a number of former or wavering Green voters.
Jim Coyle, 65, said he had consistently voted Green and had voted Labour once.
A retired IT consultant, he said he would lose a lot of money if TOP's policies were implemented. He would pay tax on his assets, and his superannuation would be cut in half.
But he was voting for Morgan because he was "extremely concerned" about his children and future grandchildren: "I have no idea how they are ever going to be able to buy a house."
Doris Zuur, 59, a former principal, said she was attending her first TOP event after following the party's progress online.
A Green Party supporter, she said she was thinking of voting TOP because of its tax on assets and its universal basic income.
"I am impressed. [TOP] is values-based, not about celebrity. And I am looking for content."
She was worried, however, that her vote could be wasted if TOP did not reach the 5 per cent threshold.
"I feel very challenged by it all because I am very loyal to the Green Party ... But [TOP] is Green Party Plus."
