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.