US Secret Service director Kimberly Cheatle resigned on Tuesday in the wake of the assassination attempt against Donald Trump at a campaign rally. Both Republicans and Democrats have been demanding that she step down over the security failures at Trump’s rally near Butler, Pennsylvania on July 13 that resulted in a bullet grazing his right ear. Cheatle had rebuffed those calls until now, including during more than four hours of tough questioning by incensed lawmakers in the House of Representatives on Monday. The representatives demanded to know how the gunman, Thomas Matthew Crooks, was able …