Three goals inside the final half-hour period of play helped Cliftonville extend an unbeaten record at Shamrock Park to over five years.
Portadown fell to a 3-0 reverse - with Cliftonville assistant manager Mal Donaghy impressed by the response from the squad to first-half frustrations.
“We spoke at half-time of the need for another five or 10 per cent,” he said. “We put a lot of work into our set-pieces so that led to the first goal then two substitutes scored to give us a well-deserved win.”
Portadown forced Jason Mooney into saves off Garry Breen’s close-range effort and a drive from distance by Matthew Parker.
A James Knowles corner-kick dropped inside the box and Jason McGuinness smashed in the loose ball.
Jude Winchester then reacted first to pick out substitute David McDaid for Cliftonville’s second goal.
Stephen Garrett stepped off the sidelines and fired number three into the top corner within moments of joining the game.
“We must take confidence from the first-half performance and the football played,” said Ports boss Pat McGibbon. “Our heads dropped once we conceded the first goal and we need to maintain our play over the course of a full game.”
PORTADOWN: McGaughey, Carson, Rodgers, O’Hara (Simpson, 71), Breen, Byrne, Garrett, Shannon, Haire, Hughes (Kirwan, 80), Parker (Ferris, 80).
Subs (not used): Miskelly, Henderson.
CLIFTONVILLE: Mooney, McGovern, Ives, McGuinness, Knowles, M.Donnelly, Hughes (McDaid, 70), Harkin (G.Donnelly, 70), Winchester, J.Donnelly (Garrett, 90), Cosgrove.
Subs (not used): Bonner, Curran.