Hillary Clinton: “It’s just awfully good that someone with the temperament of Donald Trump is not in charge of the law in our country.”

Donald Trump: “Because you’d be in jail.”

A flashback: On Sunday morning, Sept. 8, 1974, White House Press Secretary Jerry terHorst met with Jerry Ford in the Oval Office to work out the final details of a surprise presidential announcement. In little more than an hour, Ford would drop a bombshell that would ultimately cost him the 1976 election.

But first, terHorst — who like the president he served had been on the job for less than a month — had a surprise of his own. With a heavy heart, he handed Ford a letter of resignation in protest over the president’s decision.

It was the first moment that Ford had to confront the political costs of pardoning Richard Nixon. In the immediate aftermath, just 38 percent of Americans supported freeing Nixon from the threat of prison. By June 1976, that number had dwindled to 35 percent.

But over time, even militant Nixon foes came to recognize Ford’s wisdom in refusing to put a former president on trial in banana-republic style. In 2001, Ted Kennedy, on behalf of the Kennedy Library, gave Ford the Profile in Courage Award for the Nixon pardon “that made it possible for us to begin the process of healing.”

After a debate in which Donald Trump sunk to sewer depths unimagined by Nixon, how does the American political system begin the process of healing?

[Defection Saturday: A Day That Will Live in GOP Lore]

When a variant of that question was asked Sunday night, Hillary Clinton responded with a political set piece invoking her campaign slogan “Stronger Together.” She went on to say, “I want us to heal our country and bring it together because that’s, I think, the best way for us to get the future that our children and our grandchildren deserve.”

That response encapsulated Clinton’s debate: Her answers were calm and sensible, but also boring and poll-tested. Knowing that all the political currents were flowing in her direction, Clinton prudently decided to try to spend an entire debate not making waves.

Trump, of course, was the human wave machine spewing vitriol with every blowhard gust. The portion of the debate when he wallowed in Bill Clinton’s sex scandals will be remembered as another destructive battle in the bilious billionaire’s never-ending war against political decency.

With TV screen images that suggested that the hyperactive Trump was running for stalker in chief, it is difficult to imagine that the GOP nominee won back a single vote from college-educated women. In fact, female supporters of Trump in the formerly Republican upscale Philadelphia suburbs may now be so rare that they deserve their own reality show.

But Trump may have been practicing for this debate on the sly between brooding hours watching cable TV in his Fortress of Solitude at Trump Tower. After his pile-on of bile, Trump rallied in the second half of the debate, actually giving something resembling a standard Republican answer to the question about coal and energy.

[Ryan on Trump: Members Should ‘Do What’s Best for You’]

Trump was just effective enough in the debate to leave wavering Republicans with a Catch-22 dilemma: It’s too late to credibly abandon the nominee and it’s too dangerous to stick to him.

A complete debate meltdown would have given every Republican an exit strategy — saying that the former reality show host had squandered his last shot at partial redemption. But, in truth, the gangplank to depart the SS Trump was raised on Sunday afternoon. From now on, all Trump defectors will look like they waited for the polls instead of departing out of principle.

Paul Ryan — whose reputation may never fully recover from his twists over Trump — reportedly freed House Republicans on Monday morning to “do what’s best for you in your district.”

The problem is that it is impossible for any House Republican to completely separate from the GOP ticket, especially when the presidential race is overshadowing all other political contests. In fact, an NBC News/Wall Street Journal poll, released Monday, showed the Democrats with a stunning 49-42 percent lead in the generic congressional ballot question.

While Trump’s debate threat to jail his opponent in a democratic election remains the most chilling moment in modern political history, the tarnished real estate mogul’s admission that he didn’t pay federal taxes for years may prove to be the most politically damning.

The best metaphor for the crisis of the 2016 Republican Party was witnessed by Cincinnati Enquirer reporter Chrissie Thompson. She watched the debate at the home of anguished Ohio GOP chairman Matt Borges, who was searching for a way to stick with his party’s tawdry presidential nominee.

Just at the moment when Trump defiantly dismissed the 2005 tape of his loathsome sex boasts as mere “locker room talk,” Borges’ dog threw up. Never has there been a stronger case on behalf of canine wisdom.

Roll Call columnist Walter Shapiro is a veteran of Politics Daily, USA Today, Time, Newsweek and the Washington Post. His book on his con-man great-uncle was just published: “Hustling Hitler: The Jewish Vaudevillian Who Fooled the Fuhrer.” Follow him on Twitter @MrWalterShapiro.