Taxpayers' Union director Jordan Williams filed a civil case against Craig, the former Conservative Party leader.
Williams took exception to comments made by Craig at a press conference in 2015, and in a pamphlet he published called Dirty Politics and Hidden Agendas. The pamphlet was delivered to more than 1.6 million New Zealand households.
Craig said Williams had lied about him and was part of a smear campaign to push him out of the Conservative Party leadership.
The "false accusations" he alleged Williams spread were mainly around Craig's relationship with his former press secretary Rachel MacGregor, who quit suddenly two days before the 2014 general election.
A few weeks later MacGregor told Williams she had complained to the Human Rights Commission that Craig had sexually harassed her over a long period of her employment.
She shared letters and poems the politician sent her. Williams revealed the details to other Conservative Party members.
Craig then named Williams in a group of "schemers" he said were responsible for a "plot" against him.
Williams then filed defamation proceedings in the High Court, saying he did not lie about Craig.
The trial featured several significant exchanges.
Day two: Jordan Williams on Rachel MacGregor
Details of Rachel MacGregor's shock resignation as Conservative Party press secretary and her allegations that her boss Colin Craig had sexually harassed her were revealed for the first time.
Taxpayers' Union executive director Jordan Williams told the jury that after MacGregor confided in him, he went behind her back and revealed the allegations to other Conservative Party members.
He told them about a sexual text message Craig had sent MacGregor, saying it read: "I slept well last night because I dreamt I was lying between your naked legs."
Days two and three: The Colin Craig poems
Williams revealed in court the contents of letters, poems and cards Craig wrote to MacGregor when she was his press secretary.
He said he took these to the Conservative Party members because he felt Craig was "fundamentally flawed" and the wrong person to lead a political party based on Christian family values.
He said after he read the letters from Craig he was upset, and that the contents disturbed him and made him feel "unwell".
One of the poems was titled YAWAB - an acronym for You Are Wonderful And Beautiful.
Part of the poem read:
(Please skip this section if inappropriate)
Your eyes are lovely
You look unbelievable in your new dress
Your lips are so amazing to kiss
Your skin is so soft
You have the most perfect...
(LOL...ok I deleted a couple of lines and stopped this section).
Please know that you are beautiful.
Day three: Christine Rankin's evidence
On the third day of the trial the jury heard from former Conservative Party chief executive Christine Rankin.
Williams had gone to her with the poems, letters and other information disclosed to him in confidence by MacGregor.
Rankin said she was not entirely surprised because there had been rumours and suspicion around Craig and MacGregor's relationship in the months leading to the press secretary's resignation.
Rankin said she spoke to Craig about this and was assured nothing was going on.
She confronted Craig again after speaking with Williams and Craig admitted writing "flowery" personal messages to MacGregor.
"I remember saying 'You didn't? You're stuffed,'" Rankin told the jury.
"If this got out, I thought it would ruin his career."
She went on to say there were other signs something inappropriate was going on between her party leader and his helper.
"There were many, many, many things," Rankin told the jury.
"It certainly looked as though something very unusual was going on ... I was never allowed in that office without knocking ... curtains went up ... the atmosphere, you could almost touch it, it was very embarrassing."
Day four: Williams admits he hasn't seen sext
After giving evidence that he spoke to Conservative Party members about a sexual text message sent by Craig to MacGregor, Williams revealed he had never seen such a message.
The admission came during a lengthy cross-examination by Craig's lawyer Stephen Mills, QC.
"You knew the sex text was enormously damaging to Mr Craig, and you had never read it," Mills suggested.
Williams conceded that he could not recall if he had seen the text at that stage.
"If I could say I'd read it, I would have," Williams told the jury.
Day seven: Rachel MacGregor takes the stand
For the first time since her resignation MacGregor spoke about Craig and what had led to her leaving her job.
She also confirmed that hours after she quit she filed a sexual harassment complaint against Craig with the Human Rights Commission.
She detailed the comment that prompted her resignation - revealing to the jury that Williams was effectively wrong about the sex text, but right in part about what was said to her by Craig.
MacGregor and Craig were in his car on the way to an early morning radio interview two days out from the 2014 general election.
"We initially engaged in small talk and I asked him how he had slept the night before," she told the jury.
"He said something to the effect that he had slept well the night before because he had imagined he was sleeping on my legs."
She said she was angry, uncomfortable and upset by Craig's comment.
Day nine: Colin Craig's evidence
Nine days into the trial the jury finally heard from Craig.
Reading his brief of evidence in court, he admitted an "inappropriate" relationship with MacGregor, one that was "close and affectionate".
"I considered Rachel to be like a sister to me ... I accept my affection went too far ... my behaviour was inappropriate, I regret that," he said.
Craig explained that he had told his wife about this, and she forgave him.
He also spoke about learning of MacGregor's sexual harassment complaint, saying it came as "absolute bolt out of the blue" and was very upsetting.
The jury also heard from Craig about the Human Rights Commission complaint.
He explained that he attended mediation with MacGregor and they settled their issues.
He paid what he owed her and she "dropped the sexual harassment complaint".
The pair agreed to keep the matter confidential and signed an agreement.
The court would later hear from Craig that he breached the confidentiality 12 times.
Day 10: Craig tells jury about MacGregor's "indecent proposal"
Amid explaining to the jury how he responded to Williams' "spreading false accusations" about him, Craig alleged his former press secretary had quit four days after he rejected a sexual advance from her.
Craig said the pair were on a flight and MacGregor told him she wanted to be "more" than just his press secretary.
"She told me 'I want to be with you, I want to be more than just your press secretary'. At that point it was like someone tipped a bucket of water over me," Craig said in court.
"A warm and caring conversation suddenly became very serious. I recall saying 'Rachel, don't say that' or 'Rachel, you can't say that'. I did that as firmly as I could to make it clear what she was propositioning was never going to happen, and could never happen.
"How did she think it was going to work? Did she think I was going to leave my wife? I was upset."
Day 12: Colin Craig details election night kiss
During the trial the jury heard a lot about an "incident" between Craig and MacGregor on the night of the general election in 2011.
She said he kissed her and touched her breast. He later admitted that, adding it was a consensual act and one both parties deeply regretted.
The kiss led to official "boundaries" being introduced to ensure his relationship with his press secretary stayed professional.
After Craig gave evidence and had been cross-examined by Williams' lawyer Peter McKnight, his own lawyer re-examined him.
He asked Craig to read through MacGregor's brief of evidence on the kiss - which she had not been asked to do on the stand - and address anything he felt was wrong.
"It was one of those stupid things," he said.
"No one on either side objected at the time."
He refuted suggestions he had taken off his pants in front of MacGregor but claimed she took her shirt off.
"I have never taken my pants off around her," he said.
He said he could not remember her having a bra on, rather her shirt had a built-in bra.
Neither party was naked, he told the court.
He also claimed MacGregor tried to "fondle" him.
"But I stopped her. Tired and silly. I wouldn't put anything more down to it than that," he said.
"Something had happened that shouldn't have happened. We both knew that."
Day 15: Williams' outburst
On the final day of evidence Williams was recalled to the stand.
Craig's lawyers wanted to question him further on a series of Facebook messages sent between him and blogger Cameron Slater.
The messages related to a political news story that happened well before the MacGregor resignation.
In the email Williams makes inappropriate remarks about a female friend, suggesting how he could elicit information from her for the purpose of a story.
Mills put to Williams that using his friends for his own political agenda was something he had done before.
"For pursuit of your own political agenda, you are prepared to use people who are your friends for those wider political objectives," Mills said.
Williams became emotional and angry on the stand.
He denied he had "used" MacGregor by calling her as a witness at the trial, and said he had tried his best to protect her.
He called Craig, sitting in the public gallery, a "prick" and then directed his anger at Mills.
"You shat on Rachel in this case," he said. "You couldn't help yourself."
Williams' recall marked the end of the evidence.