Sen. Elizabeth Warren has become something of a hero in progressive circles. A longtime consumer advocate, Warren has been a lion in the Senate, defending citizens against cronyism and corruption in Washington and on Wall Street. She’s as tireless an advocate as you’ll find in politics, and her reputation among liberals has only grown in recent years.Observers have waited impatiently for her to weigh in on the presidential campaign. Will she endorse Clinton or Sanders? Generally speaking, political endorsements count for very little. Warren is an exception, though. She has real clout. If she puts her stamp on a candidate, it matters.Although she’s been careful not to make an official endorsement, it seemed obvious enough that Warren would back Sanders. They’re perfectly aligned on every issue of consequence, and a Warren endorsement of Clinton would seem unavoidably expedient.