However, he told IGN: "Last year, Don (Jon Hamm) has a more favorable eye on [Pete] and so [the audience] have a more favorable eye on him. That tells you that they're following the story in the way that it should be followed, which is through the eyes of the protagonist."
Kartheiser credited Pete's development to the writers of the AMC period drama.
"They've been able to take a character and show both sides of him," he said. "They've done that with every character. They've been able to show you the good and the bad and the noble and the disloyal and the cowardly and strong."
The star also described the characters of Mad Men as "paradoxes wrapped in an enigma".
"We all encompass all of it," he claimed. "Don Draper seems like an amazing man who's unbeatable, but he's a coward who ran away from war."
Mad Men airs on Sundays on AMC in the US, and Tuesdays on Sky Atlantic in the UK.