Rushden sealed promotion and pushed Carlisle deeper into relegation trouble with victory at Brunton Park.
Goals from Stuart Wardley and Andy Edwards set up Rushden's victory, which saw Brian Talbot's side climb above Hartlepool at the top of the table.
Wardley drilled home the opener in the 54th minute with a left-foot shot from the edge of the area after Marcus Bignot cleverly dummied Duane Darby's pass.
Central defender Andy Edwards then headed the second nine minutes later from Andy Burgess' free-kick, awarded following a rash tackle by Mark Birch close to the by-line.
Carlisle pulled a goal back in the 80th minute when Stuart Green turned home Brian Wake's right-wing cross but they had Mark Summerbell sent off five minutes from time after a rash challenge on Wardley.
Carlisle: Glennon, Birch, Kelly, Murphy, Maddison, McCarthy,
McDonagh, Summerbell, Rundle, Russell, Farrell. Subs: Andrews,
Wake, Green, Baldacchino, Keen.
Rushden & D'monds: Turley, Bignot, Hunter, Edwards, Underwood,
Hall, Wardley, Burgess, Gray, Holdsworth, Darby. Subs: Mills,
Bell, Sambrook, Duffy, Dempster.
Referee: S Mathieson (Cheshire)