A single goal from Jamie Murphy proved enough for the Blades, fourth at the start of the day, to overcome promotion rivals Bournemouth 1-0 at Dean Court. The result saw the Cherries slip from second to sixth but the battle remains tight with just two points separating them from the new leaders.
Swindon, who began the day top but still in turmoil following the departure of manager Paolo di Canio and a number of his backroom staff, slipped to second after being held 1-1 at Preston.
Adam Rooney claimed the equaliser for the Robins moments after coming off the bench, cancelling out Preston's first goal under new manager Simon Grayson, scored by Will Hayhurst.
Tranmere moved from sixth to third on the back of a 5-1 win at Colchester. Max Power, Jean-Louis Akpa Akpro, Ash Taylor, Cole Stockton and Michael O'Halloran - the latter from the penalty spot - were all on target in a convincing performance from the Wirral side. Colchester's solitary effort came from Magnus Okuonghae.
Two other promotion contenders, Doncaster and Yeovil, played out a 1-1 draw at the Keepmoat Stadium, while Portsmouth remain rooted to the foot of the table after a 1-0 defeat to FA Cup heroes Oldham at Boundary Park.
Former Everton player Jose Baxter scored for the Latics early on while Pompey's misery was compounded by the sending off of Sam Sodje.
James Poole and Jonathan Franks scored as fellow relegation battlers Hartlepool secured a vital 2-1 win at Scunthorpe. James Alabi scored in reply for the Iron, while Marvin Morgan grabbed the winner four minutes from time as Shrewsbury beat Stevenage 2-1 at New Meadow. The Shrews had trailed to a James Dunne goal but Paul Parry levelled.
Crewe, three days after putting Coventry out of the Johnstone's Paint Trophy, beat the Sky Blues again. Brentford and Walsall fought out a goalless draw at Griffin Park while Crawley won 1-0 at Leyton Orient with an early Billy Clarke strike.
Substitute Mark Beck scored an 85th-minute equaliser as Carlisle snatched a 1-1 draw at home to MK Dons, who had led through Adam Chicksen.
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