Quote from Elder Law Prof Blog:
So you want to help. What do you do? "If you are considering helping someone with dementia to participate in an election, and they have registered to vote, in most cases there are only two real guidelines to keep in mind.
"After reminding the person that Election Day is nearing, ask whether he or she would like to vote."
If the answer is no, you are done.
If the answer is yes, then "you may read the voter the ballot choices, if he or she cannot read them, but cannot provide additional information or interpretation, although discussions before voting begins are permitted.
“Ask them their choices and see if they answer,” ... “If they do, they vote.”