The only title that eluded him was the 500m time trial, where he finished second behind Lewis Eccles.
Already this week, Stewart has banked the time trial gold he missed out on last year, and last night's 2000m individual pursuit.
"It's been pretty good, Southland always puts on a good week," Stewart said.
"I got a few medals last year and I wanted to keep that going this year [but] it's a long week and anything can happen." Stewart's father is an ironman competitor and he followed his sister Kate into cycling at a young age.
He hopes to make a New Zealand road team being selected for a trip to Australia this year and also has ambitions for the track.
"Short term I'd like to go to junior worlds and then onto the worlds and maybe the Olympics," he said.
A Year 11 pupil at top cycling school Palmerston North Boys' High, Stewart has been inspired by the BikeNZ track team at the world championships in Colombia last week.
Olympic riders like Aaron Gate, Simon van Velthooven and Jesse Sergent are amongst his heroes.
"All week I was getting updates and then watching it when I got home from school. Seeing those sprint boys getting that gold just made it more realistic and made you feel like it can happen." New Zealand under-19 coach Ross Machejefski said Stewart was showing the sort of speed which New Zealand teams pursuit riders Pieter Bulling and Dylan Kennett displayed as they went through the age groups a couple of years ago.
"At this stage he could be sprint or endurance, it could go either way but he's probably leaning towards endurance." Stewart will be in line for selection in the New Zealand under-19 team for the Oceania championships in Adelaide in October, Machejefski said.
Meanwhile, Southland's Erin Criglington got a chance to wear her masters world championship rainbow jersey in front of her home crowd when she defended her national W1 individual pursuit title.
Criglington improved on her morning qualifying time by a second but was still about a second outside of her own New Zealand record in the final.
Wanaka's Ellesse Andrews continued an impressive first national championship, having only taken up track riding at the end of last year.
She added a bronze in the W17 individual pursuit last night to the silver she won in the 500m time-trial on Wednesday.
The national age-group championships continue until Sunday.
Today's programme, which starts from 10am and again from 6.30pm tonight, includes more individual pursuiting and the final events in the under-19 men's and women's omnium.
Day two results: W2 2000m individual pursuit: Megan Blatchford (WCNI) 1; Shona McGrath (Can) 2; Sonya Barton (Sld) 2.55.623 3.
W1 2000m individual pursuit: Erin Criglington (Sld) 2.33.769 1; Kylea Gough (Sld) 2; Nicola Stevens (Sld) 3.
W17 2000m individual pursuit:Michaela Drummond (WCNI) 2.38.271 1; Madeleine Park (Akl) 2.40.957 2; Ellesse Andrews (Sld) 2.40.876 3.
M17 2000m individual pursuit: Campbell Stewart (WCNI) 2.19.795 1; Tom Sexton (Sld) 2.24.377 2; Carne Groube (WCNI) 2.23.932 3.
W15 5km points race: Sophie Boxham (WCNI) 1; Jenna Merrick (Akl) 2; Samantha Ogle (Can) 3.
M15 7.5km points race: Corbin Strong (Sld) 1; Jamie Leitch (Akl) 2; George Jackson (Wel) 3.
M3 7.5km points race: Neil Familton (Sld) 3; Graham Bunn (WBP) 2; Ray Robinson (Sld) 3.
M2 15km points race: Garry Smith (Sld) 1; Craig Scott (Can) 2; Brett Slater (Akl) 3.
M1 20km points race:Reon Park (MSC) 1; Stu Crooks (Ota) 2; Andrew Lienert (Sld) 3.
- © Courtesy Nathan Burdon Fairfax NZ News