Correction Appended The former Yonkers mayor, John Spencer, defeated Kathleen Troia McFarland last night in a fiercely contested Republican primary for United States Senate, setting the stage for an uphill struggle against Senator Hillary Rodham Clinton. As widely expected, Mrs. Clinton soundly defeated her Democratic opponent, Jonathan Tasini, based on unofficial returns. With 98 percent of precincts reporting, Mr. Spencer had 60.2 percent of the vote, to Ms. McFarland’s 39.8 percent. The Republican race, which devolved into personal attacks involving marital infidelity, out-of-wedlock children, mental stability and personal revelations about past parental abuse, inspired little turnout. Last night, during his...