President Trump could have used his inaugural speech to soothe the bitter partisan divide that is undermining our country.

He could have followed the lead of George W. Bush, who - like Trump - lost the popular vote in a contested election. In his first inaugural, Bush thanked Vice President Al Gore for "a contest conducted with spirit and ended with grace." A Trump nod to Hillary Clinton, and to the 66 million Americans who gave her their vote, would have offered some hope to those who fear him.

Instead, the new president delivered a dark version of his stump speech, addressed to "all Americans" but clearly pitched to his base.

Trump portrayed a grim America preyed on by immigrants and gangs and strewn with rusted factories. He blamed "the ravages of other countries" for "ripping the wealth" from our middle class. Even more disturbing, his "America first" message promised a new isolationism that will harm our allies and encourage our adversaries.

The president's angry populism can whip up his followers, but it won't make (or keep) America great. On the contrary, it will only rip the country further apart and weaken our democratic system. And it could destabilize the entire world.

On the home front, in classic populist tones, Trump proclaimed that Jan. 20, 2017, was "the day the people became the rulers of this nation again." But who is "the people"? Do they include the 66 million who chose his opponent or the massive crowds of protesters who marched Saturday in Washington, Philadelphia, and other cities, in protest against reactionary Trump positions on women.

Jan-Werner Müller writes, in his new book, What Is Populism?, that the classic populist leader "must claim a part of the people is the people" and that only he "authentically represents this true people. When [populists] are in power there is no such thing as a legitimate opposition."

So far Trump fits that definition, with his fondness for autocrats like Vladimir Putin and his hope to hold military parades on Pennsylvania Avenue. Ditto for his classic populist denunciation of the D.C. "elite" for despoiling "the people" (although, having stacked his cabinet with ethically challenged fat cats, this blame game reeks of hypocrisy).

So the lost opportunity for outreach in his inaugural doesn't bode well for the future. A leader with magnanimity and vision might move the country forward with bipartisan cooperation on measures like rebuilding infrastructure. But a divisive populist promises bad news at home and abroad.

Indeed, foreign leaders were watching Trump's inaugural as closely as Americans for signals of what to expect from his presidency. Those signals were not reassuring.

Trump's "America First" doctrine - on trade, taxes, immigration, foreign affairs - may sound reasonable to his base. But, as Trump portrayed it, it has dangerous connotations for America's economy and its place in the world.

One of the more astonishing sentences in the speech was this: "Protection will lead to great prosperity and strength." But putting up tariffs and starting trade wars, notably with China as Trump has suggested, has huge downsides. It will cost millions of jobs and jack up prices for goods, something Trump never admitted. Nor did he mention that whole categories of manufacturing jobs have been replaced by technology and are gone for good.

So it's fine to seek better trade deals, but dishonest promises to "bring back our jobs" will lead only to disappointment. A cycle of harsh rhetoric against China - let alone trade wars - could have harsh consequences. All the more so since Trump's positions on China, and those of some of his appointees, have raised the possibility of a military conflict with Beijing.

Trump's protectionist worldview is unnerving for other reasons. He views his foreign-policy role primarily as promoting America's economic interests (and fighting terrorism). Those who complain that President Obama abdicated global leadership ain't seen nothing yet if Trump turns his back on old allies - as well as global treaties and organizations. Into that vacuum Moscow and Beijing are eager to move. Ditto for Iran.

Yet, as the inaugural hinted, Trump has scant use for America's allies, with zero appreciation of the values they share with America, and their role in protecting U.S. security interests. On the other hand, he's eager to join forces with Russia, in the (mistaken) belief that Moscow will help America eradicate Islamic terrorism "completely." (Since such terrorism revolves around ideology, not just territory, that is another promise Trump will be unable to keep.)

What's so scary about Trump's speech is that it is full of such promises. A populist needs to blame someone when he fails, and the president's inaugural indicates he will maintain a healthy list of enemies. Any hope that he might be a uniter rather than a divider looks dim after this speech.