Mitt Romney’s surprising New Year’s Day column criticizing Donald Trump was a brave, bold, and bracing corrective for a president run amok.

Romney’s first paragraph lays out his case well: “The Trump presidency made a deep descent in December. The departures of Defense Secretary Jim Mattis and White House Chief of Staff John F. Kelly, the appointment of senior persons of lesser experience, the abandonment of allies who fight beside us, and the president’s thoughtless claim that America has long been a 'sucker' in world affairs all defined his presidency down.”

If anything, though, Romney’s bill of particulars could have been longer. Trump badly misplayed his hand on funding for a border wall, making it less likely that he will secure barrier financing while spurring an embarrassing partial government shutdown. (Democratic leaders are negotiating in bad faith, and I believe they are also wrong on the substance, but that’s another story.) Trump also roiled investment markets with ill-timed and ill-considered criticisms of the Federal Reserve.

Abroad, he also made our mission in Iraq harder by appearing to snub Iraq’s leaders at a time when they are struggling to maintain crucial local support for that mission. His supposed breakthrough for peace with North Korea keeps looking more and more like the foolhardy claims of a sucker. And he continues to impose tariffs on metals from Canada and Mexico despite his utterly overhyped new trade deal, hurting American consumers while making congressional confirmation of the deal more difficult.

And those are just the worst of the lowlights.

The bigger and more important point of Romney’s column, however, wasn’t about specific Trumpian actions. Whatever are Trump’s policy errors (or successes), they are at least matched by this: “To a great degree, a presidency shapes the public character of the nation,” wrote Romney. “A president should unite us and inspire us to follow ‘our better angels.’ A president should demonstrate the essential qualities of honesty and integrity, and elevate the national discourse with comity and mutual respect. ... And it is in this province where the incumbent’s shortfall has been most glaring.”

It is of course true that the precipitous decline in the quality public discourse is far from being the fault only of this president. Still, it is undeniable that the Oval Office is a primary source.

Some people say this vitriol is needed to “win” against the Left, and some even find it entertaining. They are wrong. The open scoffing at decent discourse, the ubiquitous reliance on flagrant falsehoods, and the open disregard for ordinary standards of conduct, all erode civil society to an increasingly dangerous degree.

Until now, just about every Republican elected official who dared “call out” Donald Trump has been politically crushed. Romney, however, has national standing, and a safe seat for six years — guaranteed to last until Trump is gone. This verbal shot at Trump, as Romney enters the Senate from Utah, has at least a chance of emboldening other Republicans to work harder to rein in Trump’s excesses. More power to him.