A voter who places so much emphasis on a particular issue that where a candidate or party stands on that issue becomes the deciding factor in who they vote for.

This approach to voting can and often does result in a decrease in the voter's satisfaction with the system. This is at least partially because their candidate or party probably votes against their wishes on many issues whereas their candidate or party typically votes for the single-issue very infrequently. In the long term, this dissatisfaction can have a corrosive effect on the system as a whole.