Amanda Seyfried has been working for two decades, getting leading roles in enormously successful films like “Mamma Mia!” But the 35-year-old actor has never been a serious awards contender until now for her supporting performance as Marion Davies in “Mank.” The film from director David Fincher about “Citizen Kane” screenwriter Herman J. Mankiewicz is currently available on Netflix. Ten years ago, Seyfried said, she’d probably have downplayed something like getting her first ever Golden Globe nomination. Now she’s not afraid to admit that she’s excited. She knows that nominations and wins can mean more and better opportunities. The Golden Globes air on Sunday.