When U.S. presidential candidate Ted Cruz withdrew from a fundraiser in Texas, his wife Heidi stepped in to charm donors. A major backer uses her whenever she needs to close a deal. Another is planning a women's only event featuring Mrs. Cruz. Heidi Cruz, a Harvard Business School graduate and former Bush administration official, has emerged as a central figure in her husband's campaign, charming on-the-fence donors while acting as a bridge to the Republican establishment. The effort to broaden Ted Cruz's appeal is crucial as he soars in the polls. He has long had a strong base of support...