On May 8, 2006, about 1230 Pacific daylight time, a McKenzie Lancair experimental IV-P Turbine, N5M, veered off the runway after the left main gear collapsed on landing at Montgomery Field, San Diego, California. The pilot/owner was operating the airplane under the provisions of 14 CFR Part 91. The private pilot was not injured; the airplane sustained substantial damage. The cross-country personal flight departed Phoenix Deer Valley, Phoenix, Arizona, about 1130, with a planned destination of Montgomery Field. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot submitted a written report. He was cleared to land on runway 28L at Montgomery Field. He lowered the landing gear in preparation for landing, and received an indication of three green lights confirming that the gear was down and locked. At this point, an electrical power failure occurred, and he initiated a go-around. He turned the emergency battery on, and this restored power to the radio. The gear lights indicated that only two were down and locked. He asked the tower controller to confirm the gear position. The tower said it appeared to be down, and cleared the pilot to land on runway 28R. Upon touchdown the left main gear collapsed. The pilot stated that he should have tried to pump the gear in an attempt to get it in the locked position.