The correct answer to this open question is the following.
Unfortunately, you did not attach the sample or the photograph of the ballot. Without the image we do not what you are talking about.
Yo neither mention the election date. It could be any.
However, trying to help you, we did some research and can comment on the following.
If you are referring to the ballot issue of the November 2002 election in Florida, then we can say the following.
The design flaw in the ballot that could lead to voter confusion is the "yes and no" arrows. Yes, these arrows are not well aligned and can provoke confusion in voters at the moment they are about to make their decisions.
This ballot is so important because you express your vote preferences right there. So the most important characteristic should be clarity so people don't be confused.
So the most important suggestion is for the design of a simple, clear, colored ballot that clearly separates lines, arrows, and columns to differentiate the names of the candidates.