(Tigard, OR)  --  Police are investigating politically-related vandalism at an elementary school in Tigard.  Authorities say swastikas and derogatory messages about Donald Trump and Hillary Clinton were scrawled with a black marker at Alberta Rider Elementary over the weekend.  School officials tell KATU-TV a majority of the graffiti was cleaned up by the time students began arriving yesterday morning.  Security is being increased at the school, and a 500-dollar reward is being offered for information leading to an arrest.