When televangelist Pat Robertson supported legalizing marijuana last year, pot backers put his picture on an electronic billboard in Colorado. McClatchy Newspapers report that marijuana billboards have popped up along busy freeways from Seattle to Florida. In September, one greeted fans going to Mile High Stadium in Denver for the NFL opener. In July, pot supporters tried to get a video ad on a jumbo screen outside a NASCAR event in Indianapolis, but objections forced them to pull it. In the latest twist, pro-pot billboards are emblazoned on city buses in Portland, Maine, to win votes for a ballot measure Tuesday that would make the city the first on the East Coast to legalize marijuana for recreational use. Critics fear that the increased advertising is a sign of things to come as support for legalization continues to grow, reflected by a new Gallup poll that found backing from a record high 58 percent of Americans. They see the stepped-up promotion as a dangerous trend that will lead to more drug abuse among children.