The 52-year-old Virginia native is famous for his roles on TV's "The 4400," "Once and Again" and Crime Story." He plays flawed, but decent mayoral candidate Darren Richmond on "The Killing," the critically acclaimed, slow-boiling series about the labyrinthine investigation into the killing of Rosie Larsen, a high-school student and possible high-class call girl.
At the end of the first season, Richmond was arrested as a suspect in the slaying, then cleared by police, only to be shot by a friend of Rosie's family.
When Season 2 began this month, Richmond was still hospitalized, paralyzed from the waist down, with his political career in tatters and Rosie's killer was still on the loose.
"Last season was amazing and, in the back of my mind, I wondered: 'How in the world are they going to top this? How are they even going to do as well as this in a second season?'" Campbell told United Press International in a recent phone interview. "But I have to say they absolutely have raised the bar again. ... They have topped themselves. As intense as last season was, this season is even more so."
The actor downplayed criticism regarding the pacing of the show and the fact some people weren't happy the Larsen murder mystery wasn't wrapped up at the end of the first season to make way for a fresh story in Season 2.
"New blood is always exciting, but I'm not ready to be done with the characters or the story yet," Campbell said. "I'm not sure that the reaction to last season wasn't a little overblown. I think most people were incredibly into the story and are incredibly ready for the return. ... If they didn't like it, they wouldn't have been quite so passionate about it. I would be very, very surprised if most of those people, who most passionately voiced their disapproval of the ending, failed to tune in for the new season."
Noting how most traditional crime dramas are plot-driven and short on character, he called "The Killing" "an amazing mix of the two things."
He also pointed out how many police procedurals focus on the victim, the perpetrators and the investigators, ignoring the numerous others impacted by a murder. "The Killing" examines not only Rosie's life, but also those of her family members, friends and teachers, as well as the police trying to catch whoever stuffed her in a trunk and drowned her, and the officials running the city where she died.
"The victim of a violent crime is not the only victim," he reasoned. "Most crime shows give that short shrift. It's focused on the police work, the courtroom work and what have you. In this show, the people who are left behind after the murder of a loved one are an integral part of the story."
So, how difficult is it to leave behind Richmond, a workaholic recent widower, when filming stops for the day?
"I leave him behind when the cameras turn off," Campbell assured.
As for what's next for his character, the actor insisted he doesn't mind not knowing where he is ultimately heading.
"It really isn't important," he said. "In fact, I don't want to know what's next. Part of the joy of the job for me is reading the new script. It's rather like getting the new chapter to a really juicy novel. I make a big deal of it. I make a cup of tea, I light a fire and I sit down and read it. It's like reading the next chapter of a great, juicy novel -- only I'm in it!"
He admitted knowing what comes next might affect his performance.
"Part of the happiness of this job is not knowing and having to play the character right down the middle of the road. I don't know if he did it or didn't do it. I just don't know, so I can't tip anyone off," he said.
The show co-stars Mireille Enos as Sarah Linden, the lead homicide detective on the case, and Joel Kinnaman as her new partner, a recovering drug addict named Stephen Holder.