WASHINGTON (AP) — There were all the trappings of a campaign endorsement rally: the cheering crowds, the American flags, and the sitting president heaping praise on a fellow Democrat. All that was missing was the campaign. Three days after new Housing and Urban Development Secretary Julian Castro was sworn in, President Barack Obama paid a rare visit Thursday to the agency's colossal concrete headquarters to welcome Castro aboard. In gushing terms, Obama lavished admiration on the fresh-faced former mayor who Democrats are already eyeing as a potential vice presidential candidate in 2016. "He's young, he's good-looking, he talks good. You...