Senator Ted Cruz of Texas said on Friday that Donald J. Trump bore responsibility for “creating an environment” that encourages violence at his events. Speaking to reporters at a local Republican dinner outside Chicago, where Mr. Trump had just canceled a rally amid fierce confrontations between his supporters and protesters, Mr. Cruz began by saying that the “protesters who took violence into their own hands” were responsible for the episode. “But in any campaign, responsibility starts at the top,” Mr. Cruz continued. “And when you have a campaign that disrespects the voters, when you have a campaign that affirmatively encourages...