Remember, going negative is an effort to suppress turnout for the opposition. Trump voters are much more likely to wait until election day to vote, she gets extra time to convince them to just stay home, to not overcome everyday obstacles or just focus on other things.

If thinking about Trumps failing mental health makes a potential Trump voter uncomfortable, they might just be a little too busy or too tired or too stressed out about other things to deal with the cognitive dissonance of going to the polls to choose him.

It doesn’t need to work on a lot of people, but shaving off a fractional percent in key states could make a big difference.