'65 Dart No brake lights. Brake light switch failure?

The main problems to look for:

No power, power not reaching proper points at proper times as in switch problems, bad connections, or odd things like a shorted lamp causing power feedback to wrong circuits. Switches can do that too, if the switch contacts start "wandering around" inside

CHECK POWER when calling for "in operation." If flasher won't cycle, try making a jumper with male "spade/ flag" terminals so you can plug a jumper in across the flasher socket.

Test for power TO the brake light switch, and AT BOTH HALVES of the turn signal switch connector. Wiggle the hazard switch, wiggle the TS switch. Determine if brake lamp(s) work on each or one or either side. Get a helper or erect mirrors so you can see the lamps

CHECK sockets for grounding, and remove and clean and inspect AND TEST lamps. Lamps should be 1157 or 1034 or some form similar, with DUAL contacs and OFFSET bayonet pins. TEST the lamps to make sure both filaments light AND that ONLY ONE lights on each contact. (Testing for internally crossed filaments)