No elec. power to my 66 Dart

Wouldn't you know, I drive my '66 Dart to a benefit show our CC was helping with and when I go to start it no elec. power.....period.....nada...........zip. The horn works but other than that, nothing. It has a 273 in it and everthing in the car worked perfect aside from the sending unit. We found it would crank just fine if we jumped the relay, but no fire. No headlights, dome, signals, radio, nor click when key turned. We checked the wiring and found it to be good. We are wondering if it isn't the ignition switch.

I has an alt. gauge that shows charge/discharge, can this cause problems? The needle on it was bumping around on the high end of the charge side on the way to the show.

Thanks in advance.