The finding that majority preferences can be cyclic: a majority prefers A to B, another majority prefers B to C, and a third prefers C to A, so no option beats all others.
In more detail
With three voters ranking A>B>C, B>C>A and C>A>B, A beats B 2 to 1, B beats C 2 to 1, and C beats A 2 to 1. Condorcet noted such cycles in 1785. An option that beats every rival head to head is a Condorcet winner, and it may not exist. Condorcet methods differ in how they pick a winner when cycles occur. How often cycles arise in real elections is an empirical question.