After Derby boss Paul Clement was widely criticised following his side's slow start to the season, the former Chelsea, Real Madrid and Paris Saint-Germain assistant coach has masterminded an impressive revival.
The Rams have lost just twice in 23 second-tier matches and are firmly in contention for a place in the Premier League after their latest dominant display.
Jacob Butterfield fired home six minutes from time to see off struggling Fulham after an unfortunate Tim Ream own goal had given the hosts a 52nd-minute lead.
It was enough for Clement's side to move one point clear at the top after overnight leaders Middlesbrough saw their Boxing Day trip to Blackburn postponed due to a waterlogged pitch.
Hull moved up to third after a 3-0 win over fellow promotion candidates Burnley at the KC Stadium.
After a tight first half, Jake Livermore opened the scoring for the Tigers in the 57th minute with a crashing volley past Clarets keeper Tom Heaton.
An equally fine finish from Uruguayan striker Abel Hernandez extended the home side's lead before Sam Clucas put the gloss on the performance with a third in injury time.
Stuttering Brighton dropped to fourth after being held to a goalless draw by Brentford at Griffin Park.
Ipswich held on to the final play-off place after an injury-time header from Luke Chambers gave Mick McCarthy's men a 2-1 home win over QPR.
The game looked to be heading for a draw after Junior Hoilett's header on the stroke of half-time was cancelled out by a close-range effort from Jonathan Douglas.
But captain Chambers had other ideas and seized the points when he met a Freddie Sears cross and directed the ball into the bottom corner.
Sheffield Wednesday also kept up their play-off push with a 3-0 win over Birmingham at Hillsborough, two goals from Fernando Forestieri sandwiching a second-half effort from Kieran Lee.
At the bottom, Bolton's crisis-hit season went from bad to worse as they were hammered 4-0 at fellow strugglers Rotherham to fall seven points from safety.
Harry Lennon's injury-time equaliser gave second-bottom Charlton a valuable point at Bristol City, for whom Nathan Baker had grabbed a 45th-minute lead.
Huddersfield eased to a 3-1 win over Preston and Josh Murphy scored a last-minute winner to give Milton Keynes Dons a 2-1 victory against Cardiff.