Sen. Hillary Rodham Clinton made it clear Wednesday that she is not going away just because of an underwhelming victory in Indiana and an overwhelming defeat in North Carolina. No surprise there. Resiliency, defiance and a high threshold for shame have been among the defining traits of the Clintons' political life. "I'm staying in this race until there's a nominee," she told reporters in Shepherdstown, W. Va. She has every right to stay in the race. There may be an unwritten rule that candidates should drop out and rally around their party nominee when the math becomes implausible, but the...