CHICAGO — Lance Armstrong finally cracked.

Not while expressing deep remorse or regrets, though there was plenty of that in Friday night’s second part of Armstrong’s interview with Oprah Winfrey.

It wasn’t over the $75 million in sponsorship deals that evaporated over the course of two days, or having to walk away from the Livestrong cancer charity he founded and called his “sixth child.” It wasn’t even about his lifetime ban from competition, though he said that was more than he deserved.

It was another bit of collateral damage that Armstrong said he wasn’t prepared to deal with.

“I saw my son defending me and saying, ‘That’s not true. What you’re saying about my dad is not true,”’ Armstrong recalled.

“That’s when I knew I had to tell him.”

Armstrong was near tears at that point, referring to 13-year-old Luke, the oldest of his five children. He blinked, looked away from Winfrey and, with his lip trembling, struggled to compose himself.

It came just past the midpoint of the hourlong program on Winfrey’s OWN network. In the first part, broadcast Thursday, the disgraced cycling champion admitted using performance-enhancing drugs when he won seven straight Tour de France titles.

Critics said he hadn’t been contrite enough in the first half of the interview, which was taped Monday in Austin, but Armstrong seemed to lose his composure when Winfrey zeroed in on the emotional drama involving his personal life.

“What did you say?” Winfrey asked.

“I said, ‘Listen, there’s been a lot of questions about your dad. My career. Whether I doped or did not dope. I’ve always denied that and I’ve always been ruthless and defiant about that. You guys have seen that. That’s probably why you trusted me on it.’ Which makes it even sicker,” Armstrong said.

“And, uh, I told Luke, I said,” and here Armstrong paused for a long time to collect himself, “I said, ‘Don’t defend me anymore. Don’t.’

“He said OK. He just said, ‘Look, I love you. You’re my dad. This won’t change that.”

Winfrey also drew Armstrong out on his ex-wife, Kristin, whom he claimed knew just enough about both the doping and lying to ask him to stop. He credited her with making him promise that his comeback in 2009 would be drug-free.

“She said to me, ‘You can do it under one condition: That you never cross that line again,”’ Armstrong recalled.

“The line of drugs?” Winfrey asked.

“Yes. And I said, ‘You’ve got a deal,”’ he replied. “And I never would have betrayed that with her.”

A U.S. Anti-Doping Agency report that exposed Armstrong as the leader of an elaborate doping scheme on his U.S. Postal Service cycling team included witness statements from at least three former teammates who said Kristin Armstrong participated in or at least knew about doping on the teams and knew team code names for EPO kept in her refrigerator. Postal rider Jonathan Vaughters testified that she handed riders cortisone pills wrapped in foil.

Armstrong said in the first part of the interview that he had stayed clean in the comeback, a claim that runs counter to the USADA report.

And that wasn’t the only portion of the interview likely to rile anti-doping officials.

Winfrey asked Armstrong about a “60 Minutes Sports” interview in which USADA chief executive Travis Tygart said a representative of the cyclist had offered a donation that the agency turned down.

“Were you trying to pay off USADA?” she asked.

“No, that’s not true,” he replied, repeating, “That is not true.”

Winfrey asks the question three more times, in different forms.

“That is not true,” he insisted.

USADA spokeswoman Annie Skinner replied in a statement: “We stand by the facts both in the reasoned decision and in the ‘60 Minutes’ interview.”

Armstrong has talked with USADA officials, and a meeting with Tygart near the Denver airport reportedly ended in an argument over the possibility of modifying the lifetime ban. A person familiar with those conversations said Armstrong could provide information that might get his ban reduced to eight years. By then, he would be 49. The person spoke on condition of anonymity because he was discussing a confidential matter.

After retiring from cycling in 2011, Armstrong returned to triathlons, where he began his professional career as a teenager, and he has told people he’s desperate to get back.

Winfrey asked if that was why he agreed to the interview.

“If you’re asking me, do I want to compete again ... the answer is hell, yes,” Armstrong said. “I’m a competitor. It’s what I’ve done my whole life. I love to train. I love to race. I love to toe the line — and I don’t expect it to happen.”

Yet just three questions later, a flash of the old Armstrong emerged.

“Frankly,” he said, “this may not be the most popular answer, but I think I deserve it. Maybe not right now ... (but) if I could go back to that time and say, ‘OK, you’re trading my story for a six-month suspension?’ Because that’s what people got.”

“What other people got?” Winfrey asked.

“What everybody got,” he replied.

Eleven former Armstrong teammates, including several who previously tested positive for PEDs, testified about the USPS team’s doping scheme in exchange for more lenient punishments. Armstrong said in the first part of the interview that he knew his “fate was sealed” when his most trusted lieutenant, George Hincapie, who was alongside him for all seven Tour wins between 1999-2005, was forced to give Armstrong up to anti-doping authorities,

“So I got a death penalty and they got ... six months,” Armstrong resumed. “I’m not saying that that’s unfair, necessarily, but I’m saying it’s different.”

Armstrong said the most “humbling” moment in the aftermath of the USADA report was leaving Livestrong lest his association damage the foundation’s ability to raise money and continue its advocacy programs on behalf of cancer victims.

Originally called the Lance Armstrong Foundation, the cyclist created it the year after he was diagnosed with a form of testicular cancer that had spread to his brain and lungs. Doctors gave him 50-50 odds of surviving.