WASHINGTON — A Donald Trump supporter aired unsubstantiated rumors of Ted Cruz infidelity on CNN on Friday. Within an hour, Cruz accused Trump of using “henchmen” to peddle tabloid “garbage” and “complete and utter lies.” By mid-afternoon, Trump took to social media to deny his involvement in the story. Mainstream news outlets had steered clear of the rumors and a report in the tabloid National Enquirer before the Trump supporter — appearing live with Amanda Carpenter, a CNN commentator who had worked as Cruz’s communications director — demanded Carpenter address the allegation that she had an affair with the senator....