South Carolina GOP Senate primary heads to a runoff

Sen. Darline Graham advanced Tuesday to a runoff in South Carolina's crowded Republican Senate primary, extending the fight to succeed the late Sen. Lindsey Graham. Her opponent is not yet determined. Why it matters: The Aug. 25 runoff will almost certainly determine South Carolina's next senator. President Trump endorsed Graham shortly after she formally entered the race. The eventual Republican nominee will be heavily favored against Democrat Annie Andrews in November in one of the nation's…