Arriving at the crease at 14 for two, with 671 to his name in his five previous innings and nine successive 50-plus scores against England, Smith again made up for his side's top-order deficiencies with 59 not out.
England had earlier lost their last two wickets for 23 to be 294 all out and, without Smith's continuing brilliance, that might have looked a formidable score.
David Warner's series has been every bit as dire as Smith's has been successful but his latest dismissal, given caught behind off Jofra Archer via DRS only for the UltraEdge technology to be questioned, invited further inquiry.
England lasted little more than 20 minutes after resuming on 271 for eight, Jos Buttler bowled for 70 aiming a big swing at Pat Cummins and Mitch Marsh completing his maiden five-wicket haul after Jack Leach played on for 21.
The start of the Australia innings restored Warner to the spotlight, an increasingly uncomfortable place for the combative opener in recent weeks.
He came to the crease on the back of three successive ducks – signified by a trio of England fans in the appropriate fancy dress – having been dismissed six times in eight innings by Broad.
It was almost seven in nine when he hung his bat in hopeless pursuit of a wide ball in the first over of the reply but instead it was Archer who sent him on his way.
It was a curious dismissal, with umpire Marais Erasmus turning down the initial appeal for caught behind and Archer appearing to accept the decision. The slip cordon were convinced though, with Joe Root calling for DRS and a definitive spike on UltraEdge appearing just as ball passed bat.
That sealed his fate, even though the replays alone did not seem to tally up. Sceptics quickly began poring over the images to isolate the source of the noise but by then Warner was walking off with another failure on his CV.
If he felt hard done by the cameras picked up on a possible equaliser in the very next over, Marnus Labuschagne following a Broad delivery down leg side. There was no appeal of note but once again a spike appeared.
Archer started well, welcoming him with a 90mph bouncer and beating an airy drive with his second ball, before Root decided to look at Sam Curran's left-arm swing.
The all-rounder hit some good areas, Labuschagne edging agonisingly wide of Stokes on 15 and Smith surviving successive lbw appeals as he got his angles wrong but a third wicket proved elusive.
The afternoon session saw Australia add 92 for two, with Smith the unavoidable centre-point. Archer kicked off with a hostile spell of 90mph bowling, landing a painful blow on Labuschagne's elbow and forcing him on the back foot and pinning him lbw for 48.
Smith settled inevitably into his quirky, idiosyncratic groove and ticked past 700 runs for the series with a square push for four off Archer.
Matthew Wade kept him company for 31 balls and 19 runs before he was lbw to Curran, who was enjoying a fascinating but unsuccessful tussle with Smith.
The latter's 50 came up with his first real show of outright aggression, launching Leach high over wide long-on for six, and Marsh saw things through to tea.