Don Draper’s rival

The first time Kevin Rahm stepped into a popular TV series mid-run, he knew he’d be playing a major character. That was in 2005 during CBS’ “Judging Amy.” But Rahm’s next two big TV roles on mature series — gay househusband Lee McDermott on the ABC smash “Desperate Housewives” and, currently, creative rabble-rouser Ted Chaough on the AMC hit “Mad Men” — were originally scoped to be mere guest shots.

“Yeah, ‘Housewives’ and ‘Mad Men’ were both supposed to be ‘a couple of episodes each,’” says Rahm, as he makes himself some morning coffee in his Los Angeles kitchen. “‘Housewives’ turned out to be fiftysomething episodes. And this one will be as many as they let me.”

So might this be Kevin Rahm’s thing? Will he always be the life of the party who charms his way into the host’s guest room…indefinitely? “God I hope so,” Rahm answers. “I guess I’m the parasite that way.”

Actually, in previous seasons, “parasite” is a word lead mad man Don Draper (Jon Hamm) might have used to describe Rahm’s character, a nemesis from a competing ad agency who poached Draper’s accounts along with his best copywriter, Peggy Olson (Elisabeth Moss). And let’s not even bring up the time Chaough prank-called Draper, channeling the voice of Bobby Kennedy (remember, this was the 1960s — before Caller ID).

This season, though, Chaough evolved from that hard-to-reach leech on Draper’s ass to a modern-thinking partner: Draper and Chaough’s agencies merged to win a new Chevrolet account (which will turn out to be the Chevy Vega, according to Internet carstorians). And Rahm — as Rahm is want to do — graduates to playing a major fully-fleshed character.

AMC is even campaigning to nab Rahm a Supporting Actor Emmy. What kind of dramatics Rahm will perform to deserve such a nomination, he won’t reveal. “Every time I do an interview, I imagine [‘Mad Men’ creator] Matthew Weiner is in the room with me — and he’s giving me really bad looks,” Rahm says of the information-leak-proof-seal enforced by Weiner. As for AMC’s Emmy push, “I would just say that they probably wouldn’t do it unless they thought there was something good coming,” he says.

This much we can already see: As Don Draper lumbers toward the dinosaur wing of the American Museum of Natural History, Ted Chaough evolves with the 1960s, gauging the margarine marketplace with “Gilligan’s Island” castaways; giving his underlings credit where credit’s due; using the word “groovy.” (“I know, right?” Rahm gushes. “It was the first time it was used on the show — that I’m aware of.”)

The strange thing is, Chaough’s not some young upstart — he’s roughly the same age as Draper (Rahm and Draper actor Jon Hamm are both 42). So why is Chaough so late-’60s while Draper’s so early-’60s?

“I think it has to do with their upbringing, their back stories,” says Rahm. “There are really big differences between the two guys. With Draper, I think it has to do with him having to protect himself growing up. Now he’s moving past his age — my favorite was when he put on that Beatles album and was like, ‘What is this?’ Whereas, I think Ted has been freer to be whatever he needs to be.”

So, what then, exactly, is Chaough’s background?

“Yeah, I don’t know,” Rahm answers. “That hasn’t been part of the discussion. And if I did know, I couldn’t tell you.”

What Rahm can tell us relates to what we’ve already seen. “Ted will be a foil for Don in a different way than Don’s had before,” he says. As for a potential romance with Peggy Olson (they’ve already kissed), if you’re like Peggy, Ted may have given you the wrong idea.

“Based on the information we have now, I think that kiss was more out of gratitude,” explains Rahm. “He was in a dark place at that moment —his partner, who helped him create, had cancer. And there was the fear of, without that friend, can he keep doing the work? So when her response was strong, there was so much thankfulness that it was just an inappropriate response to the gratitude. And respect for her work. And she’s a hot girl — C’mon!”

In real life, Rahm has his own hot girl: Amy Lonkar, a pediatric thoracic surgeon he married just over a year ago, thanks to a setup by mutual friends in his native Louisiana. “I married up,” notes Rahm. They wed on a soundstage in Burbank, and you can still peruse their Macys.com bridal registry.

With “Mad Men” shooting finished for the season, Rahm plans to spend his summer “working on my handicap. Also, Amy’s up for a job, and we don’t know where it’s going to be. So it’ll be nice to have the summer to spend with her and get settled wherever she’s going to be.”

Which means all those TV commercial voiceovers will still be Jon Hamm’s territory. For now, at least.

MAD MEN

Tonight, 10 p.m., AMC