The article includes spoilers for the most recent episode of “Succession.”

One of the most impressive tricks HBO’s “Succession” has played on viewers over the course of four seasons is generating sympathy for reprehensible people. Sunday’s episode, in which democracy is discarded, apparently because Roman Roy (Kieran Culkin) had to eat too much chicken as a child, puts most of that sympathy to rest.

It also ended the ludicrous presidential campaign of Connor Roy (Alan Ruck), the eldest and most bumbling Roy son, who launched his bid to confront what he saw as America’s biggest problems: “usury and onanism.” But even in conceding, Connor insults voters and issues a veiled threat to unleash the “Conheads,” his followers, after saying that he wouldn’t stoop to petty behavior. It was perhaps the darkest moment for a character who has largely been relegated to buffoon status, but Ruck sees Connor’s ignorance as his main political tool.

“He’ll believe whatever sounds good to him that day,” Ruck said in a recent video call full of vivid anecdotes and laughter. “He’ll read something online or he’ll hear something on television, then that’ll become, like, the central plank of his platform for that day. And then tomorrow could be something completely different because he’s just not a focused person.”

As Connor, Ruck, 66, has spun decades of character-actor chops into some of the series’s most scene-stealing moments: the “hyperdecanting” of a bottle of wine in a Vitamix blender; the rage over butter texture while overseeing his father’s gala ceremony; the suggestion to his call-girl-turned-fiancée, Willa (Justine Lupe), that they have “razor wire and bum fights” at their wedding to gin up fanfare for his presidential campaign.

“Hands down the best writing I’ve ever encountered, week after week,” he said. “But I do think that it’d be fun to move on to something else after playing basically the family [expletive], you know, for what amounted to six years.”

Ruck sees the series as “a gift” in a career that has often been feast or famine, with occasional day jobs to pay the bills. In 1986, he played Cameron Frye in “Ferris Bueller’s Day Off”— a quintessential Gen X character in a quintessential Gen X teen comedy. But the role didn’t immediately translate into stardom, and Ruck found Cameron’s shadow to be quite long.

“There were a lot of spotty years where I was just, like, basically making just enough money to stay alive,” he said. “When people would come up during that period and say something about ‘Ferris Bueller’ it would kind of really irritate me because I felt, well, that was it. That was my shot.”

Of “Succession,” he said, “I dreamed about a show like this for years.”

Growing up in a suburb of Cleveland, Ruck found solace in acting once he reached high school. As a student at the University of Illinois, he said, he spent most of his time on a stage. The college’s performing arts complex was designed by Max Abramovitz, the architect behind David Geffen Hall, but “there was another sort of student theater that was just a small theatrical space in an armory,” Ruck said. “They’d give you a budget of 25 bucks, and you could put on any play you wanted. So it’s just a lot of experience over a short period of time.”

He moved to Chicago in 1979, a time when the theater scene, anchored by companies like Steppenwolf and the Wisdom Bridge, was beginning to take off. And after the box office success of “The Blues Brothers” (1980), he said, Hollywood became more interested in the city, making it an ideal place to be a budding actor.

“You could walk into any talent agency on a Wednesday, and just say, ‘Hi, I’m new,’ and they’d sit down and talk with you,” he said. “Talk about this with people who started in New York or Los Angeles, and they’re like, ‘What are you talking about? You can’t just go see somebody.’ So it was like the top of the minors.”

When Broadway casting directors came to Chicago to audition actors for Neil Simon’s “Biloxi Blues,” Ruck eventually landed a role. He moved to New York and shared the stage with Matthew Broderick, his future “Ferris Bueller” co-star, who remembered Ruck as having that “aura of the ‘Chicago good actor’ thing.”

“He had the look of somebody like a James Dean,” Broderick said, laughing. “Everybody in that play, we all had, like, very different personalities. But we all really did turn into kind of a unit, and Alan was a hugely important part of that.”

It was during that run of “Biloxi Blues” that casting began for “Ferris Bueller’s Day Off.” Ruck had met the director, John Hughes, in Chicago when he auditioned for an early version of “The Breakfast Club,” and his agent put his name in for the role of Cameron. But the casting directors thought Ruck, then 28, was too old.

“But then he came in and read and just sort of knocked John Hughes out,” Broderick said. “Everybody just thought he was perfect.”

“Ferris Bueller” was a hit and remains widely beloved nearly four decades later. But three years after starring in it, Ruck was working in the sorting room of a Sears shipping warehouse in East Los Angeles. He had moved to the city after landing a pilot with Nell Carter for NBC, but it failed, and he had a wife and young daughter to support.

His co-workers had no knowledge of his acting career, he said. One day as Ruck was smoking in the break room, one co-worker pointed him out to another. “He said, ‘You ever see that movie ‘Ferret Buford’s Day Off’?” Ruck recalled, laughing. “‘That looks like the [expletive] with the dad car!’”

Ruck eventually found plenty of sitcom and dramatic TV roles, most prominently in ABC’s “Spin City,” and landed bit parts in films like “Young Guns II,” “Speed” and “Twister.” It’s the type of trajectory that can be hard on an actor’s ego and paycheck but gives them space to sharpen. For Ruck, it showed him exactly what he was looking for.

“I worked on a sitcom for, you know, 18 episodes, and then there was nothing for a year,” he said. “So that gets pretty discouraging, because you’re not doing what you’re supposed to do.”

By the time “Succession” was casting in 2016, Ruck, who is now married to the actress Mireille Enos, had settled into more of a rhythm, taking whatever parts came to him. He was filming the Fox series “The Exorcist” in Chicago and flying home to Los Angeles on the weekends, while Enos was pulling 16-hour days filming “The Catch” and caring for their two young children. One weekend she asked him to join her and their 2-year-old son at a music class before he flew back to Chicago. Then he got a call from his agent: There was an audition for an HBO show, but he’d have to miss the class.

“I turned to Mireille and I said, ‘Honey, I have an audition for an HBO show,’ and she burst into tears,” he said. So he kept his promise: “We went to music class, and we banged tambourines for like an hour.” Then he stopped by the “Succession” executive producer Adam McKay’s house on his way to the airport and auditioned in his living room.

With no time to read the script in advance, he was told to improvise, which proved handy once he got the job and filming started. Mark Mylod, a “Succession” director and executive producer, said Ruck’s understanding of Connor’s delusional worldview brought “this beautiful soul to the character.” This was especially apparent during what Mylod called “freebies,” or extra takes in which the actors try alternate lines or improvise their own.

“Alan is brilliant at that,” Mylod said. “You give him a freebie and basically he could run a 10-minute roll of film without ever breaking character.”

Most of Ruck’s scenes are with Lupe, many of them excruciatingly awkward. But as their characters’ relationship grew into something more than merely transactional, Lupe said, their offscreen dynamic solidified. They texted each other regularly about how to make their scenes illustrate that evolution.

“That was really helpful” she said. “We felt like we could do it together, instead of having to create a whole narrative on my own, or him having to create a whole narrative on his own.”

Lupe pointed out their wedding scene from earlier this season. It amounted to only a few seconds of screen time in an episode destined to be remembered by viewers for the death of the paterfamilias, Logan Roy (Brian Cox). But what Lupe recalls is the emotional intensity of the filming of Willa and Connor’s nuptials.

“We had vows that we exchanged with each other that kind of helped us get to the place where that felt like an authentic presentation,” she said. “In between takes, Alan would say these things like about how great it was to work together and about how the run had been with each other. And I was just like, ‘No, don’t! I’m gonna cry!’”

Next up for Ruck are roles in two films: “The Burial,” a legal drama with Jamie Foxx, and a sequel to “Wind River.”. And while he will miss the camaraderie of the cast and crew of “Succession,” he feels he’s gotten everything he could out of Connor Roy — and some things he could do without.

“It’s weird when you play a character that’s so easily dismissible,” he said, laughing. “People continually call you ‘moron.’ You know, it gets under your skin a little bit — I’ll be happy to let that go.”