Can a Democrat vote in republican primary in SC?

In any state, they won't know what you vote. Vote how you feel. They know people change their minds. It's only human to want to change your mind.

A general election allows all voters to choose whichever candidate or law they see fit. The primary process varies across a state. In a closed Republican primary, only registered Republicans can vote in the election for Republican candidates. In an open Republican primary, any registered voter can vote for Republican candidates. In a general election, any registered voter can vote or a candidate of their choice, which can be a Democrat.