Silkmen stormed to a 3-0 lead with two strikes from Graham Potter and a goal from Matthew Tipton.
Danny Whitaker's own goal at the death reduced the deficit, when goalkeeper Alan Fettis parried a shot into his path, meaning they stay above United on goals scored - with both sides boasting a goal difference of +18.
Glovers boss Gary Johnson said: "You can't blame it on a reaction after the Charlton FA Cup game.
"If we'd faded in the last half-hour then you might have pointed to that, but we got stronger as the game went on. I just felt we were too weak; weak willed, weak physically.
"These boys can recover and will recover but they'll have to do it soon if teams like Macclesfield aren't to catch us up."
Lincoln maintained their promotion bid with a comprehensive 3-0 win against Oxford at Sincil Bank.
Simon Yeo scored from the penalty spot after 31 minutes and rounded off the scoring in injury time after Gareth Taylor-Fletcher added a second.
Bobby Petta capped off an impressive debut for Darlington with the only goal of the game against Bury.
The former Feyenoord and Celtic player struck after 29 minutes, latching onto Brian Close's cross inside the six-yard area.
Cheltenham beat Rochdale 2-0, with Martin Devaney scoring either side of half-time.
Bristol Rovers blitzed Grimsby, with James Hunt, Ryan Williams and Richard Walker scoring in a 3-0 win.
Strugglers Shrewsbury stunned Leyton Orient with a 4-1 win, and Chester eased past Rushden and Diamonds 3-1.
Prolific Boston striker Andy Kirk hit a late double to seal a 2-1 win over Boston.
Richie Barker scored the winner for Mansfield against Notts County in front of a crowd of more than 10,000 at Meadow Lane.