What's interesting is that SCP implements consensus without electing a leader. There are, of course, numerous asynchronous protocols that do this, like Ben Or, Rabin, Mostéfaoui, and most recently HoneyBadger, but is rarer for synchronous protocols like SCP. However, it is necessary for SCP's setting, because if you don't even have agreement among nodes over what nodes do and don't exist in the system, how could you hope to elect a leader.

One way to view how SCP avoids leader election is to consider that it is effectively emulating the leader. SCP has two phases, a nomination and a balloting phase. The nomination phase is effectively like one or more instances of an asynchronous broadcast protocol (which don't require a leader since multiple nodes can choose to broadcast). The balloting phase is like Paxos, except that the value to propose is embedded in the ballot number so nodes don't require a leader to tell them what is being proposed--they can each emulate the leader themselves.