Cardiff have choked more often than the Boston Strangler and five points from five games in March had conjured visions of them missing out on promotion yet again. But they put that dip behind them in emphatic fashion to reassert their authority at the top of the table.

They are 11 points clear of third-placed Watford, whom they play at Vicarage Road on Saturday. Malky Mackay and his team need 11 points from their final seven matches to be certain of a place in the top division for the first time in 50 years.

Blackburn were simply dreadful, a disparate collection of low-morale individuals rather than a team. They are now without a win in their last 10 games and must be odds-on to go down. Their distress is a classic reminder to fans everywhere to be careful of what they wish for.

When Rovers supporters hastened Steve Kean's departure at the end of September they were third in the table, having been top the previous week. Today, after five managers in the same season, only goal difference is keeping them out of the bottom three.

They used three former England midfielders – David Bentley, Danny Murphy and David Dunn – but were feeble throughout. Bentley was so poor he had to be substituted to spare him further embarrassment.

Mackay reacted to Cardiff's 2-1 defeat at Peterborough on Saturday by doing what was once unthinkable: dropping Peter Whittingham, who for years has been regarded as the best midfielder outside the Premier League. His place went to Kim Bo-Kyung.

Craig Bellamy, rested at London Road, returned up front and the injury-plagued Jordon Mutch reappeared in midfield for the first time since New Year's Day. The manager admitted he had never left out Whittingham before and explained that his playmaker had needed a rest, adding: "We needed a bit more energy today and what's the point in having a strong squad battling for places if you keep picking the same players all the time."

The changes had the desired effect, with Mutch impressive both in midfield and in support of Fraizer Campbell and Kim energetic and inventive.Mackay said: "It was very pleasing. We started really well and had 18 shots on target in the first half before Fraizer scored. Their goal had a charmed life for a long time but we were relentless all over the pitch, dominating from start to finish and playing some good football. We also got our 15th clean sheet of the season, which is something I'm really pleased about."

Blackburn had the ball in the net first, through Colin Kazim-Richards in the 35th minute, but from an offside position. The let-off served to spur the league leaders and after Campbell had struck the crossbar Bellamy was denied twice in the same attack, the goalkeeper Jake Kean repelling his first shot, then David Jones clearing the second off the goalline.

From the consequent corner, swung in by Bellamy from the left, Campbell scored his sixth goal in 11 appearances with a stooping header, close in at the far post. Rovers' latest manager, Gary Bowyer, claimed his goalkeeper was fouled while the ball was in the air and probably had a point.

Cardiff should have had a penalty after 74 minutes when a high kick by Murphy caught Ben Turner in the face well inside the area and the referee's assistant indicated, incorrectly, that the offence was outside. They would have had the second goal their superiority warranted 10 minutes later but for a high-class save by the substitute goalkeeper, Grzegorz Sandomierski, the Pole clawing out the header after Turner met Bellamy's cross.

It was left to another substitute, Joe Mason, to double the margin, slotting home his sixth goal of the season from Aron Gunnarsson's clever pass. In stoppage time Mason was brought down by Scott Dann forWhittingham, on for Mutch, to complete the scoring from the spot.