LOS ANGELES (Reuters) - Taylor Swift, straight off a controversial dive into U.S. politics, was the big winner at the American Music Awards on Tuesday where she used her platform to again urge her fans to get out and vote. The 28-year-old pop singer won a record fourth artist of the year trophy at the fan-voted American Music Awards, beating rappers Drake and Post Malone, as well as Britain’s Ed Sheeran and rock band Imagine Dragons for the top prize. She also picked up three other awards, for best female pop artist, best tour, and best pop album for “reputation,” the biggest seller of 2017.