You may not have heard of Julian Castro, currently Secretary of Housing and Urban Development, but you will. Hillary Clinton has him very near the top of her list for the veep slot on her ticket. It makes sense: he’s Hispanic, hard left, and the product of an elite education (Stanford, Harvard Law). So serious is the possibility that Page Six reports of him (and his brother Joaquin): “Surprisingly, they don’t speak Spanish,” one insider told me. “They are cramming with Rosetta Stone.” (A spokesman for Julián denies he is studying Spanish.) Julian was Mayor of San Antonio before he...