She was not returning phone calls or emails, he said, adding that he now did not expect to speak to her until today or after the election.
Ms Cunliffe said she believed Miss MacGregor was simply overwhelmed with the high-pressure environment of the party's campaign headquarters.
There was nothing more to the resignation, she said.
Ms Cunliffe said Mr Craig was not manipulative and she hoped voters would view Mr Craig and the party on their performance so far.
"It's hard because we are so close [to election day]. Anything like this to a party, it has to be handled very delicately.
"I think people would just love it if this became a blot on the landscape but it isn't what everyone is trying to make it out to be.
"I'm not worried.
"I think the public in general will have to look at the bigger picture and not one incident from a person from a high-pressure environment."
Ms Cunliffe said Mr Craig had remained calm and solid throughout the campaign and that quality should be considered in light of yesterday's revelations.
"People that know Colin ... they all know that we are people that represent family values."
Tauranga Conservative Party candidate Nathaniel Heslop would not comment on the matter.
Yesterday, Mr Craig expressed gratitude for all the hard work and effort Miss MacGregor had put into the campaign.
"The campaign puts stress on everyone and Miss MacGregor has been party of a wonderful team that have given 110 per cent." Miss MacGregor had not offered a reason for the resignation, which had caught Mr Craig "totally out of the blue".