Calcavecchia -- who held a three-shot advantage after Round 1 -- finished 36 holes at 8-under 136.
That was four better than his closest challenger, Kenny Perry (70).
Thirty-three golfers were forced to complete their opening rounds Saturday after a 3-hour-plus rain delay in Friday's opener.
Tied for third place at minus-3 were Esteban Toledo and Brad Faxon, each of whom fired a 5-under 67.
Fred Funk carded 69 to share fifth with a large group at minus-2.