Super Bronco mower not starting. Replaced battery and spark plug.
When I turn the key, I get nothing. No turnover, no click, nothing.

Is there a connection between the brake pedal and the starter?

Yes, the brake pedal has to be down for it to turn over. The deck must be all the way up too. You could have a blown fuse. It should be located by the solenoid. Just follow the positive cable from the battery to locate it.