Who will replace Graham?
According to South Carolina law, Gov. Henry McMaster will appoint a temporary replacement to fill Graham's seat until Jan. 3 of next year.
Unlike some states, South Carolina does not generally require the governor to appoint someone from the same political party as the senator who left office. That gives the governor broad discretion in choosing a temporary replacement.
In June, Graham defeated multiple primary challengers to secure his party's nomination as he vied for a potential fifth term. Now, a special primary must be held by Aug. 11, according to state election laws, to find a replacement nominee.
That nominee will face Democratic Dr. Annie Andrews in November.