The Republican nominee dismissed his sexually aggressive comments about women as "locker room talk." He attacked Hillary Clinton over Bill Clinton's alleged sexual misconduct. And he repeatedly made false claims and factual errors.
For Trump, it was a real improvement.
The second presidential won't catapult Trump past Clinton -- but it might save his candidacy from the cratering that appeared imminent in the 48 hours leading up to their showdown in St. Louis.
Scorching the earth
Trump called Clinton "the devil," told her if he were elected he'd appoint a special prosecutor and "you'd be in jail," and claimed Clinton has "tremendous hate in her heart."
And those weren't even his most shocking moments of the night.
Ninety minutes before the debate, Trump held a surprise event with three women who accused Bill Clinton of sexual misconduct and one woman who was 12 when Hillary Clinton was the court-appointed defendant for the man she said raped her. Trump also invited them into the debate hall as his guests. And he attacked Clinton over her husband's behavior during the debate.
"What he's done to women, there's never been anybody in the history of politics in this nation who's been so abusive to women," Trump said of Bill Clinton. "Hillary Clinton attacked those same women and attacked them viciously," he added, without providing evidence to support his claim.
This is what scorching the earth looks like.
It was even too much for Republican National Committee chairman Reince Priebus to take. "I wasn't involved and it's a campaign decision," he told CNN's Sara Murray after the debate regarding the decision to invite the four women.
Trump downplays lewd comments as 'Locker room talk'
Trump was forced at the opening of the debate to address the controversy that's torn apart the GOP and led more than two dozen high-profile Republicans to withdraw their support: his 2005 comments on a hot mic that his star status allows him to sexually assault women.
His message: It wasn't really that bad.
"This was locker room talk," Trump said. "I'm not proud of it. I apologize to my family; I apologize to the American people. Certainly I'm not proud of it, but this is locker room talk."
When co-moderator Anderson Cooper pressed Trump to say whether he's ever actually -- as he claimed in the 2005 "Access Hollywood" video -- gone up to a woman to "grab her by the pussy," Trump said, "No, I have not."
Clinton pounced, calling Trump's remarks in the video revealing.
"What we all saw and heard on Friday was Donald talking about women -- what he thinks about women, what he does to women."
Clinton used the moment to deliver a scathing attack on Trump's history of attacks on Muslims, Mexican immigrants, a disabled journalist and African-Americans.
"So, yes, this is who Donald Trump is," she said.
What stood out to many Republican political operatives about Clinton's performance is just how vulnerable the Democratic nominee is on many issues -- and how a GOP candidate other than Trump could have exploited those weaknesses.
Trump never cited Clinton's call to eventually move to open borders throughout the hemisphere -- a remark that came to light Friday in transcripts of private speeches obtained released by WikiLeaks.
It was a moderator -- not Trump -- who raised Bill Clinton's comment that Obamacare is the "craziest thing in the world."
Trump landed one clean blow when Clinton leaned awkwardly on Abraham Lincoln as she answered a question about whether it's OK to be "two-faced" and have a "public" and "private" position on issues, saying Lincoln himself used different arguments with different lawmakers to end slavery.
"She lied, and now she's blaming the lie on the late great Abraham Lincoln," Trump shot back. "Honest Abe never lied. That's the big difference between Abraham Lincoln and you."
However, Clinton was able to go mostly unscathed over controversies that should have badly damaged her.
She managed to land the punches she wanted to land, while letting Trump's performance be the story of the night. And she stood firm and showed little emotion as Trump early on delivered scathing attacks against her and her former husband's infidelities and actions.
"I pretty much saw what I expected to see," Clinton told reporters aboard her campaign plane afterward. "That's why the first thing I said, something I've been saying since June -- that he's not fit to be president and commander in chief, and there are a lot of people who said it before and increasingly more adding it to the chorus."
Trump appeals to the base, but didn't reach beyond it
The biggest problem for Trump is that even if Capitol Hill Republicans rally back to his side, he did nothing to expand his appeal to voters who don't already support him.
There was plenty of red meat -- from his lock-her-up promises to the stagecraft of his attack on Bill Clinton.
But many of his comments appeal only to a narrow subset of right-wing activists. Among them: Attacking Clinton friend Sidney Blumenthal and former Democratic National Committee Chairwoman Debbie Wasserman Schultz and repeatedly revisiting Clinton's private email server.
Those topics are gangbusters with listeners of conservative talk radio and pro-Trump loyalists who read Breitbart News and similar websites, but they do little to sway women in the Philadelphia suburbs and other voters Trump needs if he's going to win.
He also risked offending African-Americans by referring -- in response to a black man's question -- to helping the "inner city," implying it's the only place African-Americans live.
And he responded to a Muslim woman's question about Islamophobia by saying that "we have to be sure that Muslims come in and report when they see something going on. When they see hatred going on, they have to report it."
That -- and Trump's unusual posture, standing closely behind Clinton as she responded to some questions -- led to this tweet from New York-area college professor Moustafa Bayoumi going viral: "I'm a Muslim, and I would like to report a crazy man threatening a woman on a stage in Missouri."
Lock her up?!?
Trump arrived Sunday with two tricks up his sleeve: The pre-game Bill Clinton attack and a heightened attack on Clinton over her private email server.
"If I win, I am going to instruct my attorney general to get a special prosecutor to look into your situation," Trump said, "because there has never been so many lies, so much deception."
Even by 2016 standards, it was a remarkable moment -- one more befitting of an autocracy than American democracy.
Clinton attempted to turn the moment into an attack on Trump's biggest weakness -- his temperament.
"Good that someone with the temperament of Donald Trump is not in charge of the law in our country," she said.
To that, Trump shot back: "You'd be in jail."
Gone is the Donald Trump who responds to adoring crowds' chants of "Lock her up!" by saying: "Let's defeat her in November." Instead, Trump has fully embraced a much more aggressive posture that's likely to extend through the campaign's final four weeks.
In a repeat of the first debate, Trump repeatedly made inaccurate claims, and Clinton directed viewers to her website for a real-time fact check.
In Sunday night's debate, Trump blasted Clinton over taxes, accusing her of proposing to "raise taxes on everyone" when she has focused her proposed tax hikes only on the wealthy.
He claimed he'd never directed people to search for former Miss Universe Alicia Machado's (non-existent) sex tape, when on September 30 he'd denounced "disgusting (check out sex tape and past) Alicia M" on Twitter.
He said he opposed the war in Iraq, when in fact he supported the war in Iraq.
He claimed that "many people saw bombs all over the apartment" of the San Bernardino shooters, which is not true.
He falsely blamed Clinton for starting the "birtherism" controversy, when it was Trump who led the racially motivated attack on President Barack Obama for five years.
It's a reality that's baked into the cake with Trump at this point: His supporters don't take his claims literally, and Trump claims that refusing to reveal his true hand is part of what makes him a brilliant negotiator. Fact-checks mean nothing to him.
Did Trump stop the bleeding?
Forget the bigger, tougher task of convincing voters he has the character and temperament to be president for now. Trump's chief assignment Sunday night was to stop a crisis.
Ahead of the debate, running mate Mike Pence was bailing, members of Congress were denouncing him en masse and the Republican National Committee was considering cutting him off. That would have left Trump a dead nominee walking, with no get-out-the-vote operation anywhere four weeks from Election Day as others in the GOP try to save their skin.
Afterward, a CNN/ORC instant poll of debate watchers found that Clinton had won, 57% to 34%. But 63% of debate watchers said Trump had done better than they'd expected, to 21% who said he'd done worse. It wasn't a victory for Trump -- but he'd averted a total meltdown.
Trump needed to make it to the third and final debate next week in Las Vegas still a viable candidate with a shot at defeating Clinton next month. His performance will buoy his supporters -- which will make it harder for Republicans to defect and may guarantee Trump still has the infrastructure and organizational support to continue his campaign.
Still, there are signs of splits. One of the many odd moments -- and a divide to watch within the GOP moving forward -- came when Trump threw Pence under the bus. Pence had said the United States should be ready to use military force in Syria -- but Trump defended Syrian strongman Bashar al-Assad (who is backed by Russia) and called the crumbling city of Aleppo lost.
"He and I haven't spoken and I disagree," Trump said of Pence.
But Pence, at least, didn't appear ready to jump ship.
"Congrats to my running mate @realDonaldTrump on a big debate win! Proud to stand with you as we #MAGA," he tweeted.