@PamKeithFL An undervote is any ballot that lacks a vote (or complete vote) for any race/question on the ballot. An undervote is not limited to a lack of a vote for president. A voter can cast a ballot that is completely blank, and therefore, completely undervoted for every race/question.
@johnpavlovitz People choosing not to vote for president but voting for other ballot races and questions. We should compare ballots cast versus votes cast.