South Carolina is an open primary state which means Democrats are allowed to ask for a Republican Primary ballot to torpedo vote against President Trump. And of course they will in droves.
Look at the calendar:
https://www.270towin.com/2024-presidential-election-calendar/
The South Carolina Democratic primary is three weeks before the Republican primary.
Democrats with Trump Derangement Syndrome have to make a decision—vote early in the Democratic primary or wait three weeks to vote for Haley.
Most will vote in the early primary and then be ineligible to vote in the later one.