GOP voters are literally afraid of everything, that's their whole world view. They're afraid of immigrants looking for asylum, people who've left their home out of desperation. They're afraid of transgender folks, who already face all sorts of discrimination in their personal lives. The GOP is afraid of the world and so they punch down on whoever they see as weakest to make themselves feel better about themselves.
They're afraid she will encourage more people to vote. The more people who vote, the harder it is for them to game the system. That's why they pass voter suppression laws constantly.