  Liquid democracy is a decision-making paradigm in which each agent can either
vote directly for some alternative or (transitively) delegate its vote to
another agent. To mitigate the issue of delegation cycles or the concentration
of power, delegating agents might be allowed to specify multiple delegation
options. Then, a (cycle-free) delegation is selected in which each delegating
agent has exactly one representative. We study the winner determination problem
for this setting, i.e., whether we can select a delegation such that a given
alternative wins (or does not win). Moreover, we study the robustness of
winning alternatives in two ways: First, we consider whether we can make a
limited number of changes to the preferences cast by the agents such that a
given alternative becomes a winner in one/in all delegations, and second,
whether we can make a limited number of changes to a selected delegation to
make a given alternative a winner.
