The Democrat Party is searching for the next Obama. Biden was not it. Sanders is not it. And Hillary Clinton is definitely not the next great empty vessel. Obama, when he burst on the scene, was seen as a good looking and charismatic figure, who could deliver one hell of a speech, and since he's black, he'd also be a historic President. So little was known about him that the voters could also place upon him all of their hopes and dreams. He was envisioned as the perfect leader, and even after two terms of his disastrous presidency, there are still those that claim he's the best President in history.
Julian Castro fits all of those necessities the Democrats need for the next great Democrat President. Never mind that he's an unknown. With talk about him being Hillary's running mate, once his charm reaches the air waves, and Hillary's campaign falls to pieces because of all of the baggage regarding emails, Benghazi, and her constant lies exploding at once, I have no doubt the Democrat voters will demand that Julian Castro runs for President.
As the Texas Insider website said of Julian Castro, "The Hispanic politician has long been considered a rising star within Democratic political circles since his keynote speech at the 2012 Democratic National Convention."
Don't forget, it was a keynote speech at a Democratic National Convention that made Obama a rising star in the party, as well.
-- Political Pistachio Conservative News and Commentary
Julian Castro Fuels Vice Presidential Speculation - Texas Insider
Hillary Hints Julian Castro Could be V.P. Pick - New York Magazine
6 Key Exchanges from Hillary Clinton's Benghazi Testimony - Daily Signal