Platner is the latest Democratic candidate to shrug off dark revelations about their past, reflecting a new era in politics and an example set by President Donald Trump, who has forged ahead undaunted by controversies that would have been campaign-ending discoveries only a decade ago. The new revelation about Platner comes close behind the discovery of a series of controversial online statements, including one in which he dismissed sexual assault in the military. It also follows a pattern set by Jay Jones, this year’s Democratic nominee for attorney general of Virginia, who has refused to drop out of the race...