Fifteen wickets fell yesterday but it is the next five which are most important for the Volts.
The visitors started the day in great shape but slumped from 86 without loss to be all out for 253 in reply to Auckland's first innings total of 196.
Otago's last six wickets fell for just 13 runs, with Dean Bartlett making the most of overhead conditions to claim his maiden first-class five-wicket bag.
He swung the ball beautifully but so did Otago's attack. Neil Wagner and Ian Butler grabbed two wickets apiece as Auckland crashed to 96 for five.
The home side's recovery will rest with Colin Munro, fresh from a remarkable undefeated double hundred against Wellington last week, and 20-year-old Craig Cachopa, who has made a promising start to his first-class career.
The pair combined in a massive 377-run stand for the sixth wicket against Wellington and will resume with Auckland 118 for five and nursing a slender lead of 61 runs.
"We've had a disappointing batting display... but, to be fair, our bowlers have bowled as well if not better than Auckland," Otago coach Vaughn Johnson said.
"But we still have a big job to do in the morning. We need to stick to our lengths and bowling plans and get these wickets."
Aaron Redmond was the standout for Otago. He resumed undefeated on 23, with Hamish Rutherford on 60.
The pair were looking to press on and build a substantial first innings lead. That plan began to unravel when Rutherford was run out on 70.
Michael Bracewell worked hard for his 17 before he was bowled by veteran left-arm spinner Bruce Martin and Neil Broom and Nathan McCullum nicked out in quick succession.
Otago was still reasonably placed at lunch on 162 for four but the gradual decline picked up pace when Sam Wells was dismissed for 38. He had combined in an 82-run stand for the fifth wicket with Redmond, but his departure triggered a rapid collapse.
Derek de Boorder (5), Redmond (98) and Ian Butler (0) were all removed from the batting crease with the score stuck on 246.
Redmond might have missed out on what would have been his third 100 this season but Johnson thought it was one of his better innings for the province.
"Aaron's innings was one of the finest he has played for Otago - I would go that far. He batted a lots of balls and showed a lot of guts in working through some tough situations and making sure he stayed parked up at one end today. I thought he did that really well."
Auckland made a brisk start to its second innings with Lou Vincent whacking 38 from 27 deliveries. But before he could do more damage Butler found the edge of Vincent's bat and followed up by dismissing Tim McIntosh in similar fashion.
Wagner rattled the home side further, dismissing Colin de Grandhomme and Gareth Hopkins, and Jimmy Neesham enticed former New Zealand keeper Reece Young into a mistake to leave Auckland with a lot of work to avoid defeat today.
Meanwhile, rain may have washed out most of the first day of Northern Districts' match against Canterbury, but a result is very much in play, APNZ reported.
The defending champion Knights would have been surprised to take a first-innings lead after slumping from 125 for two to 200 all out, but they will resume today 130 runs ahead with seven wickets in hand.
That is because Canterbury's batsmen found life even more difficult on a decent track at Seddon Park, and were dismissed 14 runs short of the host's total.
At stumps, ND was 116 for three.
