According to the South Carolina website:
A Resident is an individual that is domiciled in South Carolina or an individual who intends to maintain a home in South Carolina and South Carolina is the center of their financial, social and family life.
A Nonresident is an individual that has a permanent home outside of South Carolina and the definition of resident does not apply.
A Part-Year Resident is an individual that moved into or out of the state during the tax year. This individual qualifies as a resident for only a portion of the tax year. You may choose the residency status that is the most beneficial for you when filing your return.
What if I am a resident but my spouse is not?
If a joint federal return was filed and one spouse is a resident of South Carolina and the other is not, file a joint South Carolina nonresident return. The resident spouse must report all income while the nonresident spouse reports only the income earned in the state.
If you file separate federal returns n (MFS), you & your spouse must file a separate South Carolina return if they have income taxable by South Carolina.
For more information: