A performance-variable bushing includes an inner support element and an outer support element. An elastomeric connecting element extends between and operatively connect the inner and outer support elements such that a substantially fluid-tight seal is formed therebetween. The elastomeric connecting element can be at least partially formed from one of an electrorheological elastomeric material and a magnetorheological elastomeric material. The performance-variable bushing includes a variation-inducing element operatively associated with the elastomeric connecting element and selectively operable to vary values of one or more physical properties of the elastomeric connecting element. The elastomeric connecting element is configured for use under a pre-load force from pressurized gas within a spring chamber of an associated gas spring and damper assembly. Gas spring and damper assemblies and suspension systems are also included.