The pilot of the tailwheel-equipped airplane reported that, during the initial climb, the engine began to run abnormally and lose RPM. While troubleshooting, he noted the right magneto dropped by about 500 RPM. Unable to correct the malfunction, he chose to return to the departure airport to perform a precautionary landing. During the landing roll, the airplane veered to the right, while correcting with rudder and brake, the airplane veered to the left and subsequently nosed over. The airplane sustained substantial damage to the right wing lift strut and rudder. At the time of the accident, the pilot was landing the airplane on runway 14 with wind from 230° at 8 knots. Post accident examination of the ignition system revealed that the No. 3 cylinder ignition lead was degraded. The center conductor fell apart when the connector end was removed. The dielectric was worn and the center conductor was loose inside of the wire, allowing it to intermittently ground out against the shield and spring. No faults were observed with the remaining 7 leads. The reduction in engine RPM noted by the pilot was consistent with a faulty ignition lead. To facilitate recovery of the airplane, both tailwheel steering springs were disconnected by first responders from the tailwheel steering arm.