COLUMBIA, S.C. (AP) — President Joe Biden easily won South Carolina’s Democratic primary on Saturday, clinching a state he pushed to lead off his party’s nominating process after it revived his then-struggling White House bid four years ago. Biden on Saturday defeated the other long-shot Democrats on South Carolina’s ballot, including Minnesota Rep. Dean Phillips and author Marianne Williamson. His reelection campaign invested heavily in driving up turnout in what it saw as a test drive of its efforts to mobilize Black voters, a key Democratic bloc central to Biden’s chances in a likely Novemb…