Gary Hart has serious reservations about a Hillary Clinton candidacy. The prospect of a billion-dollar Clinton campaign “ought to frighten every American,” he said in an interview with POLITICO, and Democrats would be better served by a competitive primary that forced her to speak in more depth about the issues. Hart, a two-time Democratic presidential candidate, offered his opinions in a phone interview Wednesday where he also expressed admiration of Elizabeth Warren and gave advice to prospective challenger Martin O’Malley, a former Hart campaign staffer. “I like Hillary Clinton. I really appreciate what she and her husband have done …...