Before the game Stephen Kenny’s side knew they could be officially dethroned if the league leaders won away to Shamrock Rovers in Tallaght and they lost to Pat’s for the first time at home in five years.
In the end, neither scenario happened, with the Lilywhites wiping the floor with Liam Buckley’s men from the moment David McMillan’s stoppage time brace at the end of the first half put them in the ascendancy.
With Ian Bermingham sent-off in the aftermath of the penalty that opened the scoring, Dundalk showed their ruthless nature after that by clocking up their joint biggest win of the season to date.
Pat’s hopes of boosting their own survival hopes suffered a huge blow after just 13 minutes when goalkeeper Barry Murphy was stretchered off, later to be replaced by debutant Lukasz Skowron.
The visitors were fortunate not to have been behind five minutes earlier with McMillan raced onto Gannon’s pass. McMillan beat Murphy but Jordi Balk was on hand to hook of the line.
Michael Duffy was denied by a stunning stop from replacement keeper Skowron on 39 minutes. Duffy turning provider a minute later as he beat Balk to cross to the waiting McMillan but his effort was blocked on the line by Lee Desmond.
The same pair would be involved in the incident which changed the match on the stroke of half-time. McMillan went down in the box after a challenge from the centre-half, with Pat’s captain Bermingham sent-off in the aftermath, as he protested with referee Jim McKell.
McMillan then stepped up to hammer home the resultant penalty before adding a second in the fifth minute of stoppage time when he headed home Duffy’s corner.
It was all one way traffic on the restart with Dundalk adding to their lead on 50 minutes when Gannon tore in from the right to bury a shot to the bottom left hand corner.
Pat’s were by now on the ropes with Skowron pulling off a number of fine stops as Duffy was denied by the crossbar.
The fourth goal did arrive on the hour mark with Duffy breaking on the left to square for substitute Robbie Benson to lash home his 10th league goal for Dundalk.
The home side were far from finished though with Dylan Connolly bursting clear on the right to slot home his first goal for the club on 73 minutes.
Then eight minutes from time Thomas Stewart made it six by lashing high to the net after Sean Hoare’s header had come off the upright.
Rogers; Gannon, Gartland, Hoare, Grimes; Connolly, Shields (Benson 56), Clifford, Duffy; McEleney, McMillan (Stewart 68).
Murphy (Skowron 13); Desmond, Balk, Barker, Bermingham; C Byrne (Feely HT), Kelly, Garvan, O’Conor (Lunney 61), Dennehy; Fagan.
J McKell (Tipperary)