[EM] Monotonic Ordering of the Uncovered Candidates (the Landau set)
As in River we start by locking in certain defeats. As in River no candidate needs to be defeated more than once to be excluded from the winner's circle. Also as in River we lock in the strongest defeats first. We consider all defeats by cover to be stronger than defeats that are not part of the covering relation. If a candidate is covered by two or more (other) we consider the defeating candidate with the greatest approval to have the strongest defeat.
So ballots must must allow us to infer both pairwise defeats and an approval order. [Any other monotonicically generated order of the candidates may be substituted for approval if so desired.]
1. For each covered candidate X, find the highest approval candidate Y that defeats X, and lock in this defeat Y>X.