Jeb Bush has been having a hard time this week after justifying his brother’s 2003 invasion of Iraq. But the heaviest criticism did not come from his political opponent Hillary Clinton, who has been silent. It came from a 19-year-old college student, Ivy Ziedrich. After a meeting in Reno, Nev., on Wednesday, Ziedrich, a member of the local Young Democrats chapter, challenged Bush on his assertion that the Islamic State terrorist group was a consequence of the Obama administration’s withdrawal of U.S. troops from Iraq.