WASHINGTON (AP) — Former Newark, N.J., Mayor Cory Booker is starting his new job in an unusual position — a freshman Democratic senator with celebrity status.

The man Oprah Winfrey once dubbed a “rock star mayor” — he has 1.4 million followers on Twitter — was sworn in Thursday during a brief ceremony on the Senate floor. He won a special election in mid-October to fill the seat of longtime Sen. Frank Lautenberg, who died in June.