Second-placed Plymouth soared seven points clear of League Two promotion rivals Carlisle after beating the Cumbrians 2-0 at Home Park.
Playmaker Graham Carey fired Plymouth into a 21st-minute lead before Jake Jervis made it 2-0 from the spot just before half-time.
Carlisle remain third despite a third successive defeat, while Plymouth moved to within four points of leaders Doncaster.
Plymouth almost took the lead in the 15th minute but Ryan Taylor's header came crashing back off the crossbar.
But Carlisle fell behind six minutes later when Luke Joyce's defensive pass was intercepted by Carey, who exchanged passes with Taylor before sweeping home.
The hosts built on their lead in first-half stoppage time when Taylor was floored by marker Shaun Brisley and recalled forward Jervis sent goalkeeper Mark Gillespie the wrong way from the spot.
James Bailey came close to scoring for United with a stinging 52nd-minute shot that beat Argyle keeper Luke McCormick but flew just past the post.
Jervis came close to adding a third in the 75th minute, flashing an angled drive off the top of the bar.