Donald Trump is a man who likes golf.

So is Bill Clinton.

Donald Trump is a man who likes to cheat at golf.

So is Bill Clinton.

Donald Trump is a man who likes voluptuous women.

So is Bill Clinton.

Donald Trump is a man who likes to talk a lot.

So is Bill Clinton.

Donald Trump is a man who likes junk food, especially McDonald’s cheeseburgers and fries.

So was Bill Clinton, until he had to clean up his culinary act.

Trump had a few quibbles about Clinton’s more catholic taste in women and his real estate bargaining skills.

How the friendship of the mighty had fallen.

The darkest, most lurid moment in modern debate history came just a few moments into the tense spectacle.

When Jeff from Ohio on Facebook asked about the “Access Hollywood” tape, Trump dived: “If you look at Bill Clinton, it’s far worse, mine were words, his were action. Never anybody in the history of this nation has been so abusive to women.”

Trump continued, saying that Hillary had attacked those same women “viciously” and that “four of them are here tonight.”

Trump, who was nervously pacing as Hillary was glaring, noted that President Clinton was impeached, lost his license to practice law and had to pay an $850,000 fine to Paula Jones.

When Hillary rebutted, noting that you had to fact-check Trump – which she did with a Freudian slip of “fat-check” – and that no one with Trump’s temperament should be in the Oval Office. Yes, Trump shot back, because if he was president, “you’d be in jail.”

The former friendship between Trump and the Clintons was dead, once and for all.

When I interviewed him in 1999, when Bill was a disgraced but still popular president and Donald was a not-yet-disgraced plutocrat toying with the idea of running for president, Trump said this: “He handled the Monica situation disgracefully. It’s sad because he would go down as a great president if he had not had this scandal. People would have been more forgiving if he’d had an affair with a really beautiful woman of sophistication. Kennedy and Marilyn Monroe were on a different level. Now Clinton can’t get into golf clubs in Westchester. A former president begging to get in a golf club. It’s unthinkable.”

Trump also sniffed about the Clinton’s new Chappaqua house: “Very overpriced. I could have gotten him that house for $600,000 less.”

He was also unimpressed in those days with Ken Starr — “Starr’s a freak” — and Hillary’s Senate run. “The concept of the listening tour is ridiculous. People want ideas. Do you think Winston Churchill, when he was stopping Hitler, went around listening?”

But it was inevitable that Bill and Donald, larger-than-life figures who both became shooting stars in the ’80s, would find each other a decade and a half later when they were both living in New York.

Trump liked to be around powerful pols who might come in handy for business. And powerful pols liked to be around Trump, who might come in handy for donations.

And donate Trump did to the Clintons, both to the family foundation and to Hillary’s Senate campaign. Over the years, he seemed to come to genuinely like and admire both Bill and Hillary, in a transactional sort of way, praising them in public statements, making Bill a member of his Westchester golf course, inviting the Clintons to his third wedding, to Melania Knauss, a sultry Slovenian model.

During the 2008 Democratic primary, Trump blogged: “I know Hillary and I think she’d make a great president or vice president,” and in 2015, he told Joe Scarborough that Bill was his favorite president, even though he believed that Bill’s entanglements with “sundry semi-beautiful women” had dampened his success.

Up until he got in the race, Trump was friendly with the Clintons, even seeking Bill’s advice in a phone call not long before he jumped in.

But once Trump saw Hillary within his sights, the friendship ended. As far as Trump was concerned, the Clintons were the enemy, and Monica and other sordid tales from Clintonworld were, as Trump put it, “fair game.”

Last May, Trump began pummeling his former pals at a rally in Eugene, Ore. “Nobody in this country was worse than Bill Clinton with women. He was a disaster. I mean, there’s never been anybody like this and she was a total enabler. She would go after these women and destroy their lives. I mean, have you ever read what Hillary Clinton did to the women that Bill Clinton had affairs with? And they’re going after me with women. Give me a break, folks.”

At a rally in Fairfield, Conn., in mid-August, Trump brought up “that woman,” noting: “I’m so glad they kept that dress. It shows what the hell they are.”

Bill, who was still popular despite the rocky patches with Monica and the Marc Rich pardon, was angry when Trump began dragging back the old scandals over women into the spotlight.

After Trump began to slide, following his nutty focus on former Miss Universe, Alicia Machado, in the first debate, he ignored warnings from fellow Republicans and unleashed a scorpion attack on the Clintons’ treatment of women, directing surrogates to use this talking point: “Mr. Trump has never treated women the way Hillary Clinton and her husband did when they worked to destroy Bill Clinton’s accusers.”

At a New Hampshire rally a few days after the debate, Trump said: “The Clintons are the sordid past. We will be the very bright and clean future.”

When the scuzzy Billy Bush “Access Hollywood” tape was leaked, Trump first tried to brush it off as private “locker room banter.” Cornered, the pouty plutocrat lashed out, like a bag of raccoons. So in his initial statement to David Fahrenthold, who broke the story in The Washington Post, Trump immediately tried to shift blame, writing: “Bill Clinton has said far worse to me on the golf course — not even close.”

Trump had told me in an interview last June over lunch at Trump Tower that the two men had fun discussing women as they golfed.

But then the whole country got rabidly consumed and the press began covering the story as though a fiery orange comet was hitting the earth. The vice president tweeted that Trump was guilty of sexual assault, and Republicans began fleeing their nominee in droves, like “rats running across the tundra,” as the late, great Hunter Thompson used to say.

By Sunday, many Republicans and even the Wall Street Journal editorial board were saying Trump should think about dropping out, because as the paper said, “the goal has to be to save a G.O.P. Congress.”

So Trump went nuclear, in the sort of nuclear policy he understands. He held a news conference in St. Louis before the debate with Clinton accusers: Juanita Broaddrick, who claims Bill Clinton raped her; Paula Jones, who got a $850,000 settlement to drop a sexual harassment claim against Bill Clinton; Kathleen Willey, who claims that Clinton, as president, assaulted her when she was a White House volunteer; and Kathy Shelton of Arkansas, whose alleged rapist was defended by Hillary Rodham and had complaints about what she saw as Hillary’s subsequent lack of empathy.

Trump probably succeeded in rattling Hillary in the hour before the debate. But he also rattled Republicans, who found the scene desperate, dark and not exactly the shift to issues and contrition they were hoping for.

Unfortunately, the four things Trump needs to do well tonight are the four things he doesn’t have: empathy, impulse control, humility and genuine regret.

This post was updated to reflect developments during the debate.