Jon Hamm feared Rob Lowe would snag his Mad Men role after a disappointing West Wing audition

Jon Hamm acted professionally for more than six years before he appeared in his signature role of Don Draper on Mad Men.

At one point, Hamm worried that he would lose out on the job, he told The Hollywood Reporter, quite possibly to Rob Lowe, who had snapped up another part that he really wanted, that of deputy White House communications director Sam Seaborn on White House drama The West Wing.

"I got the Mad Men script, and I was like, 'S---, this is really good.' And it's a good lesson in not getting ahead of yourself because I remember thinking, 'They're never going to cast me.' Because I'd had an experience with another really good script that I read and I was like, 'I would do anything to get this part.'"

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Hamm revealed the script was for The West Wing, which aired for seven seasons, from 1999 to 2006. The drama about the goings-on inside the White House won 26 Emmys, and Lowe was nominated for a leading actor trophy in 2001. The St. Elmo's Fire star departed the show in its fourth season, although he returned for the final two episodes.

"I thought, 'I could murder this part.' And I was great in the audition, but I saw the casting director's face, and I knew this part's already cast," Hamm said. "Then it was like, 'Oh, it's Rob Lowe. Okay, I get it.' So I thought the same thing would happen on Mad Men. I'll give a great audition, and they'll give it to a movie star. The first time I went in, I was the only person auditioning, it was so early in the process. And then as I’d go back in and go back in, I started seeing names that I recognized on the sign-in sheet."

It turned out that Lowe was unofficially being considered for the advertising executive part, too.

"Rob never auditioned, but he was definitely under consideration," Hamm said. "And [creator] Matthew Weiner, God bless him, basically said, 'We can't have a superstar. If Rob Lowe plays this part, it'll be the Rob Lowe show, and we don't want that. We want it to be a mystery about who this guy is.' And to my tremendous benefit, that worked."

Hamm explained that, up to that point, he'd had a tough time getting roles.

"I just didn’t fit," said Hamm, whose parents both died before he reached adulthood. "I was the guy who was 25 but looked 35. It's like I fell between two barstools. I mean, I didn’t look like I was in high school when I was in high school. I don't know if it was losing my parents, but I looked older."

Mad Men aired from 2007 to 2015, picking up 16 Emmys, including one for Hamm, along the way.