Crawley boosted their automatic promotion hopes with three first-half goals consigning Northampton to a 3-1 loss, their third straight defeat.
The Cobblers, who replied through substitute Brett Williams at the Broadfield Stadium on Tuesday, rallied late on, twice hitting the woodwork, but the Red Devils held on to extend their unbeaten run to 12 games. Scott Neilson broke the deadlock for the hosts after 14 minutes in superb style with a 25-yard strike which goalkeeper Neal Kitson got a hand to but could not prevent from going into the top corner.
Kitson was beaten again seven minutes later when Billy Clarke cashed in on poor defending with a near-post header from six yards which went under the keeper's body. The hosts continued to dominate with Gary Alexander putting a deflected shot wide before Kitson dived low to save a drive from Neilson.
Northampton's problems increased six minutes before the break when keeper Kitson turned a deflected cross from Josh Simpson into his own net. Crawley defender Kyle McFadzean threatened shortly after the break when his header was parried by Kitson.
Substitute Williams reduced the deficit on 65 minutes by punishing a slack defence from close range following a low cross from Jake Robinson.
Williams later had a goalbound shot blocked by Charlie Wassmer and fellow substitute Toni Silva put an angled shot against the bar before Williams fired against the base of a post in stoppage time.