Definers Public Affairs has sought to discredit opponents in part by spreading misleading stories via a network of right-wing sites—and through Facebook.

When Facebook CEO Mark Zuckerberg told reporters on Thursday that the company was dropping its contract with an opposition research firm that had been hired to spread negative stories about its rivals, he adopted a moralistic tone and did his best impression of Claude Rains in Casablanca. In addition to claiming ignorance about his...

Continue Reading It’s not just Facebook. GOP-linked firm “brought oppo research to Silicon Valley”