An early strike from a Stephen McGinn goal and Kyle Lafferty double saw the Ayrshire side extend their lead over Raith to eight points, throwing Rovers’ hopes of a play-off place into doubt, with fifth-placed Partick just a point behind John McGlynn’s side, but with four games in hand.
Next week’s home match with the Jags is now a crucial one for Raith if they want to stay in the top four.
McGlynn made two changes to the side that started against Celtic in the Scottish Cup last Sunday.
Christophe Berra returned from injury to replace Kyle Benedictus who is out with a pulled hamstring, whilst new loan signing Sean Mackie made his first start with Aidan Connolly dropping to the bench.
The game kicked off and before Raith even had time to settle, the home side had taken the lead on four minutes.
A Chris Burke corner was headed off the bar by Kyle Lafferty and Stephen McGinn was quickest to the ball and knocked it into the net.
Worse was to follow as after just 12 minutes Raith fell further behind.
Fraser Murray found room in the box and played it back to the edge of the box to Lafferty whose deflected effort spun up over Jamie MacDonald to double Killie’s lead.
The game quietened down and Raith began to improve slightly though struggled to create anything of note in an attacking sense, resorting to long balls which were easily mopped up by the home side’s defence.
Half time arrived with Killie looking comfortable at two goals to the good, Raith having failed to muster a single effort on goal.
The visitors made a triple change at the break, with Jamie Gullan, Ben Williamson and Sean Mackie being replaced by Dario Zanatta, Aidan Connolly and Ethon Varian and it almost paid off immediately.
Just seconds after the restart Killie keeper Zach Hemming palmed away a cross ball from Ethan Ross straight to Sam Stanton, but it was slightly too high for the midfielder and his header went over the bar.
Rovers kept up the pressure and almost equalised when Berra hit the post with a header from a Zanatta corner.
The home side hit back and a Burke shot was easily saved by MacDonald before he did well to hold on to a Lafferty free kick shortly after.
Ross curled an effort just wide of the Killie goal before the home side added a third, which was almost a carbon copy of the second.
Euan Marray played the ball to namesake Fraser who cut back to Lafferty and the striker finished well, side footing the ball into the net for his second.
Chris Stokes had the ball in the net for Kilmarnock but was flagged offside before Hemming saved well from good strikes by Zanatta and then Stanton.
Euan Murray came close to connecting with the ball for a Killie fourth with just a couple of minutes to go, but it finished 3-0 to the home side who were well worth their victory.
It was a poor showing from Raith who were well beaten and seem as though they’ve forgotten how to win.
It’s hard to see where their next three points are going to come from.