§ 1422.21 Preferential voting.
Primary source
Verbatim text below is from the Electronic Code of Federal Regulations (eCFR), a public-domain U.S. government work. Always verify the current version with the eCFR before relying on it for any legal matter.
Full Text
In any election in which more than two choices are on the ballot and no choice receives a majority of first preferences the Board shall distribute to the two choices having the most first preferences the preferences as between those two of the other valid ballots cast. The choice receiving a majority of preferences shall be declared the winner. A labor organization which is declared the winner of the election shall be certified by the Board as the exclusive representative.
This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.