The pair is tied in 16th position as the event heads into the weekend on Hilton Head.
Leishman who played well on Sunday at the Masters after a disappointing third round, has not played all that well around the Pete Dye designed layout in his previous seven starts but he is well well enough placed to improve on his previous best of 9th in the event four years ago.
Smith finished a very impressive 15th on debut in this event two years ago when not a member of the PGA Tour and today bounced back from an early double bogey for his round of 70.
Rod Pampling was the only other Australian to make the cut, doing so right on the number.
Co leader, Donald, continued his intriguing love affair with Harbour Town Links as although he has not won there he has been six times inside the top three in his last eight starts at the RBC Heritage.
Ian Poulter and Webb Simpson are two shots behind the leaders in a share of 3rd position.