The run-off election allows a selection between the choices receiving the largest and second largest number of votes cast in the original balloting. A run-off election, in the labor relations context, is a second election conducted by the National Labor Relations Board in which no choice receives a majority of the ballots in the first poll.
As another example, a primary election is an election where voters choose who will represent their political party in the general election. When only one person is running for a political seat, there is no primary, and that candidate moves on to the general election uncontested.
If no candidate receives at least a minimum percentage of the vote in the primary election, there will be a subsequent run-off election between the top two vote getters to determine the party candidate.