After defeating nearest rivals Partick Thistle on Boxing Day, they extended their unbeaten record to nine matches by seeing off Dunfermline – also in the championship frame – 4-2 at Cappielow to put clear daylight between themselves and Thistle at the summit.
Two goals in a five-minute spell from Michael Tidser and Peter Weatherson early in the second half effectively won it against a Dunfermline side, which has now taken just one point in their last four matches.
Jim Jefferies' side started on top and Josh Falkingham was denied by Derek Gaston, who diverted the ball for a corner.
But it was a temporary let-off as Falkingham swung over the kick and Callum Morris towered above the Morton defence to direct a header beyond Gaston and give his side a ninth-minute lead.
Morton's response was swift, but Mark McLaughlin's header bounced just inches wide of the post. David O'Brien was looking dangerous for Morton in the early stages as they sniffed out the equaliser. But it was McLaughlin who came close again midway through the first half when he got his head to a Tidser free-kick only for his effort to strike the crossbar.
Morton looked increasingly dangerous as the first half wore on and scored a well-worked equaliser a minute from the break.
Kevin Rutkiewicz switched play with a fine pass to free Martin Hardie, who picked out Fouad Bachirou and he knocked the ball past Paul Gallacher from close range. Tidser then put Morton in front after 56 minutes when he beat Gallacher with a splendid left-foot shot after Bachirou laid the ball back.
Before Dunfermline had time to recover, Morton extended their lead. O'Brien played in Bachirou and, when Gallacher could not hold his shot, Weatherson was on hand to fire home the third goal.
Dunfermline, however, refused to lie down and pulled a goal back 13 minutes from time. Falkingham's shot came back off the bar, but Ryan Wallace turned in the loose ball. Tidser removed all doubt when he rounded Gallacher to score Morton's fourth with just a minute left to round off a great day's work.