CNN:
Donald Trump must rule out a third-party bid before October if he wants to compete in South Carolina’s Republican primary, a crucial test in the nominating contest.
Trump has repeatedly refused to rule out a third-party candidacy, noting that he could use the threat of an independent bid as leverage, but he cannot appear on the South Carolina primary ballot unless he pledges to support the GOP nominee in the general election.
Trump said Tuesday when asked about the rule by reporters in Iowa that his campaign is “looking into it.”