Sutton moved out of the League Two relegation zone for the first time this year with a convincing 3-1 victory over Swindon.
United secured a vital fourth league win in a row to go a point clear of Colchester, who have three games in hand.
Sutton went in front when goalkeeper Jack Bycroft's poor clearance resulted in Harry Smith's cross being headed powerfully home by Charlie Lakin in the ninth minute.
Bycroft redeemed himself by denying Lakin a second when he dived to turn away a superb 20-yard volley.
But the stopper was again at fault for the second as he fumbled Josh Coley's low cross into his own net three minutes after the restart.
Bycroft's mixed afternoon continued as he made a smart close range stop to keep out Smith's shot following a corner, but he was helpless to prevent the Sutton striker scoring with 20 minutes to go as he headed in Coley's cross at the far post.
Steve Arnold was beaten by Paul Glatzel's stoppage-time free kick as the visitors netted a consolation.