It’s impossible to imagine “The Gilded Age” without Morgan Spector as George Russell, but the actor initially had his doubts.

“It’s funny, I had watched ‘Downton,’ but I didn’t think that I would be able to do it,” Spector says of creator Julian Fellowes’ previous hit ‘Downton Abbey.’ “I didn’t think I would play in the world that Julian makes, for whatever reason. And so then when I auditioned for it and tried the material on, I was like, ‘Oh, this is actually fun.’ There’s a kind of Old Hollywood classical glamour to this that is very pleasurable to play.” 

Fun is part of what makes “The Gilded Age,” now back for its third season on HBO, such a hit with audiences (critics, meanwhile, are calling the new season the best yet). The historical drama, set in the 1880s boom period of New York City, is a softer viewing experience than even “Downton” was, and certainly than the average Sunday night HBO program.

“Often when I see things on HBO that are period, they’re like, ‘OK, we’re going to do period drama, but there’s going to be horrific violence, or it’s going to be the dirty underbelly of the world you’ve seen before.’ And this is not what this is really about,” Spector says. “It’s a much gentler universe, but it’s interesting. Maybe it’s the times we’re living in, but I think people have gravitated to, I don’t want to say the low stakes, I feel like actually this season especially, there are real stakes. But it’s something where you could just enjoy the writing and the costumes of the world, and it’s not going to leave you with a gnawing feeling of horror in your stomach on the way.”

The 44-year-old actor is Mr. Russell, a new money railroad mogul who, with his wife Bertha (Carrie Coon) and two children, ascends the ranks of New York old money society. 

“The most fun is that I get to work with Carrie Coon so much,” Spector says of his onscreen wife. “I have loved building this marriage with her and this season sort of testing that marriage with her, but just getting to act with an actor who is that good makes you better and makes it so that even the days where you turn up and you have to just do three pages of exposition, it’s a pleasure.”

“George has a kind of modernity to him in a lot of ways in terms of how he treats his wife, how he treats his daughter,” Spector continues. “There’s a kind of contemporary sensitivity that I can connect to. And then there’s also this sort of period patriarch quality to him, which in terms of an act of historical imagination is also fun to play. He’s not going to be as in touch with his feelings. He’s not going to be as willing to kind of accept doubt or weakness in self as maybe I would be. There’s a lot about investigating 19th-century masculinity that I think is fascinating.”

The upcoming season, which debuts on Sundays on HBO through Aug. 10, will see George take on more financial risks with his business life, and at home, his daughter Gladys’s potential marriage presents many questions. 

“There’s a lot at stake over the course of this season, for sure,” Spector says.