Matthew Lund, Ian Henderson and Peter Vincenti scored the goals for the League Two leaders as they registered their fourth straight victory, while Portsmouth lost their third consecutive game as they continue to battle against relegation.
Although Rochdale and their visitors on Tuesday are separated by 20 positions in the table, the home team's manager Keith Hill said his players had negotiated a tricky fixture against a side he rates highly.
"I think it's testament to the squad ... and the belief that they have in each other that we can perform like that against, what I do consider, a very good side with quality players, who are probably suffering from a lack of confidence," Hill told Rochdale's website.
"So it was a very dangerous game for us tonight and I thought we managed the game exceptionally well."
Rochdale moved to 73 points with the win, staying two ahead of second-placed Scunthorpe United, who won 2-0 at Cheltenham.
Lund gave Hill's side the lead in the 16th minute at Spotland Stadium with a close-range header, while Rochdale doubled their advantage just before the hour-mark when Henderson converted after latching onto a long ball.
Vincenti scored the hosts' third goal in the 63rd minute from Matt Done's cross, as Rochdale extended the visitors' winless streak to six matches.
The result left Portsmouth on 42 points in 22nd position, two ahead of Northampton Town, who occupy the first of two relegation spots.
Northampton could have overhauled Portsmouth but gave up a 2-1 lead against AFC Wimbledon to draw 2-2.
A brace from Darren Carter had put Northampton in front at home but the visitors from Wimbledon ruined the hosts' night when Luke Moore scored in the sixth minute of second-half stoppage time.
Towards the top of the table there were wins for Chesterfield, Fleetwood Town, Burton Albion and York City.
Third-placed Chesterfield stayed within three points of Rochdale after edging out Morecambe 1-0 thanks to James O'Shea's 19th-minute goal.
Fleetwood and Burton both moved to 64 points with wins over Bristol Rovers and Wycombe Wanderers respectively.
In Lancashire, Fleetwood made it two wins in a row at home with a 3-1 triumph over Rovers, while Burton accounted for Wycombe 1-0.
York (58 points) moved within a point of fifth-placed Oxford United - who lost on Monday - with a 1-0 triumph over bottom side Torquay United.
It was the sixth consecutive win for Nigel Worthington's men with William Hayhurst scoring in the 11th minute for York.
In other results, Mansfield Town scored three times in the final 20 minutes to overcome Hartlepool United 4-2, while Newport County were held to a 0-0 draw by Bury, Exeter City won 2-1 at Plymouth Argyle and Dagenham & Redbridge versus Accrington Stanley remained goalless.
