NEW ORLEANS — The Mercedes-Benz Superdome wasn’t plunged into darkness, but it certainly wasn’t nearly as bright as it had been a heartbeat earlier.

For as wonderful a host as New Orleans was in the Super Bowl’s return to this resilient city, and as electric the atmosphere in the Superdome was through the opening half and a high-energy halftime show by Beyonce, it all came to a halt at 7:37 p.m. local time when the giant videoboards and much of the overhead lighting in the building went out.