Most of the $1 million he donated to the party in 2014 went into nationwide leaflet drops. Each run of Conservative brochures, of which there were four, cost $180,000.
The party raised its share of the vote from 2.65 per cent in 2011 to 4.12 per cent last night, but gained no MPs because it fell below the 5 per cent threshold.
Mr Craig is already committing to another bid in 2017, though he says he will need to rebuild his own finances.
"I have to save for the next election. I'm not broke, I still own the house, I've still got a shirt on my back. And I have business interests and a profit-making company but the reality is ... we have the challenge of working out how we fund this."
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Mr Craig said his personal contributions were crucial as long as Conservatives did not have any MPs and were ineligible for Parliamentary funding.
"That's something we'd love to be able to challenge. I hate a system which says you can only have as much radio and TV time as we give you and by the way we're giving you guys 60 grand and we're giving Labour and National $1.2 million."
Mr Craig said grassroots campaigning and membership was just as important as money. This was evident in the failure of internet-Mana to get a single MP despite its wealthy backer Kim Dotcom donating around $4.5 million to the party.
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The Conservative leader would also work to keep the party's big donors onside.
Retired Hamilton multi-millionaire Laurence Day, who together with his wife Katrina gave $675,000 of their own money to the Conservative Party's campaign, said he was still feeling quietly confident about the party.
Mr Day, who received more than $10 million for his share of a private training organisation when it was sold recently, was once a National Party stalwart but now backs the Conservatives, mostly because he is a strong supporter of binding referenda.
Asked if the contribution was wasted, Mr Day said: "I put that money aside for a cause that I really believe in ... we're giving it a shot ... we've certainly put ourselves seriously on the political map, and going forward people will take us a lot more seriously."
Mr Day said he believed the strong campaign meant labels such as "fringe" could no longer apply to the Conservatives.
He would definitely support the party financially in the future, he said. National would not always have such strong support and they would now view the Conservatives as a viable support party.
"Somebody has to sow the seeds going forward."
