Disappointed Limerick fans chanted "we are staying up" for most of this game at the Markets Field, but the tune changed before the finish and Dundalk trooped off at the end with their fans singing "that's why we are champions".
Limerick took the lead inside two minutes through Dean Clarke and held firm until the final quarter of an hour, when the champions struck three times in the space of six minutes.
The home side got off to a dream start when Shane Tracy's corner was flicked on by Vinny Faherty.
After a block on the line, the ball fell for Clarke to finish from close range and most of the 2,178 paying customers erupted in jubilation.
Darren Meenan ought to have equalised in the fifth minute when through one-on-one with Limerick goalkeeper Freddy Hall but, despite the siege towards the home side's goal in the first half, there was no way past the magnificent Hall.
Dundalk again struggled to create chances after half-time before the intoduction of Ciaran Kilduff midway through the second half gave them added impetus.
And it was Kilduff who supplied Richie Towell with the chance to equalise on 76 minutes, the midfielder blasting the ball home for his 20th league goal of 2015.
After Limerick had a strong penalty appeal waved away when Clarke went down in the box, Towell doubled his tally with 10 minutes remaining when his shot on the turn deflected off Shane Duggan and left Hall stranded.
From Dundalk's next attack, Daryl Horgan's through ball to Kilduff saw him spring the Limerick offside trap and he finished coolly past Hall to secure the points for Stephen Kenny's side.
The Lilywhites now know that victory in their next assignment away to Shamrock Rovers next Friday week will clinch the title.
Limerick, meanwhile, are still bottom, but on this evidence they have a great chance of surviving.
Limerick FC - Hall; Kelly, Kanyuka, Williams, Tracy; Duggan, O'Conor (Agyemang 87); Turner, Lynch (Russell 70), Clarke; Faherty.
Dundalk - Rogers; Gannon, Barrett, Boyle, Massey; Towell, Shields (O'Donnell 63); Meenan (Mountney 75), Finn, Horgan; McMillan (Kilduff 67).
Ref - N Doyle (Dublin)