RICHMOND — Less than a year after Eric Cantor’s shocking defeat to a tea party challenger, House Speaker William J. Howell is taking nothing for granted in his first serious primary challenge in nearly three decades. The latest sign that Howell (R-Stafford) learned from the mistakes of the former majority leader of the U.S. House of Representatives came Wednesday, when the state lawmaker launched a Web site titled “We Know Bill.” It includes dozens of vignettes, complete with photos and fawning quotes, from retirees, businesspeople and activists talking about why they support Howell over his challenger, Susan Stimpson. The approach...