Campbell has frequently seen himself at odds with his co-workers and dissatisfied with his marriage to wife Trudy (Alison Brie) over the course of Mad Men's five seasons, including several severe clashes with business partner Roger Sterling (John Slattery).
In an interview with Slate, Kartheiser explained that business success will never bring Pete the happiness he craves.
"With success comes a level of sadness. You think, 'I'll reach this goal, and then I'll feel a sense of completeness, of wholeness. I'll feel that I have accomplished something. I will see myself as a worthy man'. And it doesn't really exist," Kartheiser said.
"[Pete] also has the weight of this entire agency on his shoulders, and he doesn't feel like he's getting any respect for that. I think that a bigger man would handle that better. Pete becomes pouty and kind of aggressive. He tries to show off and make people respect him, and that's not possible."
Kartheiser also said that he does hold out some hope that Pete will find happiness.
"There are times in your life where you realise the distance between who you are and who you thought of yourself as," the actor said. "Everyone's inevitably going to face periods of their life when they feel hopeless and worthless. I think there are redeeming qualities to Pete. I don't think he's doomed."
The star recently said he's glad that Mad Men fans have warmed to Pete in the last few seasons.
Mad Men airs on Sundays on AMC in the US, and Tuesdays on Sky Atlantic in the UK.
> Mad Men star Vincent Kartheiser: 'Pete, Peggy have healed wounds'
> Mad Men Rich Sommer: 'Harry would be annoying to work with'
Watch a promo for Mad Men below: