Maine Democratic Senate candidate Graham Platner has a new problem, and this one is harder to delete.New original reporting by The Wall Street Journal published Friday has tied Platner to an active profile on Kik, a messaging platform with a long and well-documented history of child exploitation, and that law enforcement officials and online safety advocates have repeatedly flagged as a danger to minors.The account, listed under the username "phustle0331," featured a mirror selfie of a towel-clad man. It was linked to other online handles associated with Platner, and remained active as recently as this week.When pressed, Platner's campaign confirmed...