Facebook is facing its toughest challenge yet: an election complicated by a pandemic, a deeply divided nation lured by conspiracy theories and alternate versions of reality. Is it ready? The company says yes. But a look back at its checkered history of trying to deal with misinformation suggests that the task could still be stickier than it seems. From its efforts to come to grips with Russian interference in the 2016 elections to the latest tweak of its policies for allowable political ads, Facebook generates a lot of rules and, sometimes, confusion.