Like a bolt from the blue, insurance company Progressive has come from “nowhere” to land atop the Media Monitors list of radio’s leading national advertisers. Progressive ran 54,890 ads around the country last week. The previous number one, Vicks, wasn’t far behind with 51,272. Rounding out the top five were GEICO (41,064), Walmart (37,279), and digital entertainment outfit Seriously (36,672). Perennial advertising giant The Home Depot reentered the top 10 at number seven with 30,986 spots.