Chesterfield had begun the day as Rochdale's closest challenger but a goalless draw at Mansfield allowed Scunthorpe to climb above them with a 1-0 win over Burton.
Paddy Madden scored the decisive goal after 60 minutes to keep the fifth-placed Brewers at arm's length.
With Fleetwood also losing, 3-0 at relegation-threatened Exeter, the top three were able to take a step closer towards automatic promotion.
Jon Parkin put through his own goal on 25 minutes before Eliot Richards struck twice in the second half for City.
York sneaked into the play-off places on the back of a 1-0 win at Portsmouth.
Michael Coulson's seventh-minute goal was enough as Pompey, now just a place above the relegation zone, had Ben Chorley sent off after 50 minutes.
York were able to climb into the top seven, on goal difference alone, after Plymouth conceded a late equaliser in a 1-1 draw at Accrington.
Tom Aldred made sure the points were shared nine minutes from the end after Reuben Reid gave Plymouth a 32nd-minute lead.
AFC Wimbledon scored three goals in as many second-half minutes to inspire a dizzying comeback in a 4-3 win over Cheltenham.
Danny Hylton struck either side of a Jake Nicholson goal in the Dons' purple patch. Jack Midson then notched the winner in injury-time.
Cheltenham had led into the 69th-minute thanks to goals from Troy Brown and Jermaine McGlashan, and even after Wimbledon's onslaught they managed a 74th-minute equaliser through Jason Taylor.
Last-placed Torquay are six points from safety following a 1-0 home loss to Newport County.
Former Gulls striker Chris Zebroski netted the winner on eight minutes and hope the home side might recover were undermined by Shamir Goodwin's 34th-minute dismissal.
Northampton edged a point closer towards safety as they drew 1-1 at Morecambe. The Cobblers led when Padraig Amond scored a 45th-minute own goal but Andrew Wright levelled 15 minutes from the end.
Bury drew 1-1 with Dagenham & Redbridge as Chris Hussey and Luke Norris traded second-half goals.
- Sports & Recreation
- Peter Vincenti
- Paddy Madden