WASHINGTON — Much of the country has never heard of Tim Scott, the junior senator from South Carolina and a presidential candidate who, at this point, is a long shot for the Republican nomination. But Democratic strategists know Scott — and some worry he might pose a real threat to beat President Joe Biden in a general election if he makes it that far. Former President Donald Trump leads — by large margins — in every Republican primary poll, but Democrats watching him appear in another courtroom are handicapping the prospects of the rest of the field. Democrats worry that...