  Consensus protocols inherently rely on the notion of leader election, in
which one or a subset of participants are temporarily elected to authorize and
announce the network's latest state. While leader election is a well studied
problem, the rise of distributed ledgers (i.e., blockchains) has led to a new
perspective on how to perform large-scale leader elections via solving a
computationally difficult puzzle (i.e., proof of work). In this paper, we
present Caucus, a large-scale leader election protocol with minimal
coordination costs that does not require the computational cost of
proof-of-work. We evaluate Caucus in terms of its security, using a new model
for blockchain-focused leader election, before testing an implementation of
Caucus on an Ethereum private network. Our experiments highlight that one
variant of Caucus costs only $0.10 per leader election if deployed on Ethereum.
