Porthmadog face an anxious final two weeks of the season after tumbling to defeat on Deeside.
Just four points ahead of Caersws in the relegation zone, Tomi Morgan's side may need a win from their one remaining game against Aberystwyth to avoid the drop.
Nomads took the lead after 11 minutes when Mike Cronshaw crossed from the right to the unmarked Danny Forde who sent a superb header past keeper Richard Harvey.
John Rowley fired over the bar and Ryan Davies hit the side netting for the visitors before Nomads doubled their lead early in the second half.
Provider Cronshaw turned poacher, cutting inside from the flank before planting his shot just inside the post. Nomads came close to scoring again on a couple of occasions through Liam Loughlin and Forde before Cronshaw put the game out of sight, tapping-in from Forde's byline cut back.
With three minutes left, Marc Lloyd Williams fired a superb 25-yarder past home keeper Terry McCormick, but it was mere consolation for the visitors who suffered a further blow when Steven Kehoe was red-carded for retaliation.
Port only escaped relegation last season on the final day of the campaign and will pray that Caersws slip-up before then to avoid another tense afternoon at The Traeth.
Stats and report courtesy of welsh-premier.com