Scunthorpe United's faltering form of late opened the door for Chesterfield to climb back to the summit, as they recorded back-to-back wins for the first time since Christmas.
Eoin Doyle broke the deadlock in the second minute of the encounter at Bootham Crescent, sending a right-footed effort into the top right-hand corner of the net.
And Gary Roberts doubled the advantage six minutes from the break to send Chesterfield top by a single point.
Oxford United, who saw manager Chris Wilder depart for basement club Northampton Town over the weekend, played out a goalless draw at Exeter City.
The point was enough to lift them to fifth in the league, with fellow play-off contenders Southend United also picking up a point at Dagenham and Redbridge.
Wilder's debut as Northampton boss will have to wait after their clash with Rochdale was rained off, along with a further three fixtures.
Bury's trip to Mansfield Town, Torquay United at home to Burton Albion and Plymouth Argyle at Newport County also fell victim to the weather.
Portsmouth picked up a first win in six matches with a 1-0 victory at Wycombe Wanderers, who are being dragged ever closer to the relegation zone.
AFC Wimbledon jumped to ninth with a 2-1 triumph over Hartlepool United, while Accrington Stanley have now suffered just one defeat in seven after winning 1-0 at Bristol Rovers.
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