This is a major problem. Voting rates are highest among the elderly, the very group at risk for dementia. Soon there will be 15 million Americans with some form of dementia.
Federal election laws give state the capacity to deny voting privileges to persons with mental incapacity. About two-thirds of the states have laws that preclude voter registration by people judged “insane" or mentally incompetent or incapacitated or who are under a guardianship order. Many of these laws are unclear and unconstitutional and none of these states identifies a standard to assess an individual's capacity to vote.
For example, Maine passed a law that bans anyone from voting if they are mentally ill to the point of guardianship. The courts struck this down as being overly broad and because it did not address the ability to vote specifically. The court articulated a standard that a person who understands the nature and effect of voting and can make a choice is competent to vote.
Guardians are allowed to assist someone in voting. But it’s illegal for them to vote on behalf of another person.
The University of Pennsylvania has a project called the
Dementia Voting Project that is attempting to address these issues and develop a procedure to determine if individuals are competent to vote.