McCartney secured a Games record at 4.65m, overtaking Kym Howe's Melbourne 2006 effort by 3cm.
However, Newman had her measure. She matched that height, then ratcheted up to 4.75m in a gamble to stay ahead. Newman cleared with what was a new personal best and national record.
Her joy was palpable as she somersaulted and grasped her forehead in relief.
McCartney made her final attempt, to no avail, at 4.80m.
"It was a good fight, because these were things I was prepared for.
"We were happy with our competition plan and we stuck to it.
"Those were big late jumps but we weren't quite making it click."
The New Zealander was the last to remove her tracksuit for competition, entering at 4.55m after one hour and 51 minutes.
She passed at 4.60m, before beginning her assault on the podium.
The evening reinforced the work of Jeremy McColl, the guru who has transformed the discipline into a world-class operation in this country at North Shore's Millennium Institute.
He offered advice from the front row of the stand.
McCartney said she was fully fit, and an advance on her personal best of 4.82m seemed possible.
She had overcome the worst of her Achilles tendon problems from last year and shaped as a gold medal contender, with the field's best vault in the world this year.
The 21-year-old cleared 4.75m on March 3 with fourth at the world indoor championships in Birmingham, and cleared the same height on March 25 in Auckland.
A week prior she arched over an unratified 4.90m on a sloping runway at the Vertical Pursuit along Federal St.
McCartney took some solace from a Dame Valerie Adams bear hug before her interview.
"She knows the hard work that's put in, and even to be out there is an accomplishment.
"I know she's proud of me, and it means a lot coming from someone with such an incredible legacy. For her to be so supportive is a moment of pride.
"I'm competing through until the middle of September, hopefully with another 10 years of a career ahead of me. This really is just the beginning."
McCartney's training partner Olivia McTaggart exited with a unsuccessful attempt at her personal best of 4.40m.
She provided entertainment with her first effort at 4.30m by dropping the pole on the runway and showcasing her gymnastics background as she somersaulted across the mat.
At 18, she was the youngest in the field. Five years ago, her training diaries revealed she wanted to represent New Zealand at a Commonwealth Games.
That was when she was a gymnast, before back problems brought a transition. She has since shadowed McCartney through the age-group ranks.
McTaggart recovered in time for the event after spraining her ankle at this month's national championships.
