As we cross the finish line of President Trump’s first 100 days, no leader in recent memory has benefited more from low expectations. A more typical president who tumbled from an approval rating in the high 60s to one in the low 40s would be in a political crisis. Trump’s current performance is only a slight dip from his divisive norm. A president with pretensions of rhetorical coherence would be embarrassed by gaffes and mediocre speeches. For Trump, gaffes and inarticulateness are part of the package. A president with high standards of integrity would be mortified by a brewing scandal that seems to involve smarmy aides and a foreign government. For Trump, well, what would you expect?

The president is particularly proud of the consequential elevation of Neil M. Gorsuch to the Supreme Court. But this action invites a comparison. Trump’s one unquestioned achievement consists of appointing another man who actually has thoughtful convictions.

Much of Trump’s 100-days defense could have been employed by the pharaoh who ruled after the one in the book of Exodus. The cattle haven’t all died. We’ve seen less fiery hail. And pestilence has been kept to an acceptable minimum.

There is, however, one area in which Trump dramatically raised national expectations. He might be unknowledgeable. He might be immature. But at least, in polling language, he is a “strong and decisive leader.” This is a conceit that becomes harder and harder to maintain.

Consider Trump’s interaction with China. On the campaign trail, the Chinese were currency manipulators who were too weak on North Korean nukes. In his first meeting with Chinese President Xi Jinping, the American president got his first glimpse of the Chinese perspective and was transformed. On North Korea: “After listening for 10 minutes, I realized it’s not so easy.” On the currency issue: “They’re not currency manipulators.” It seems the case that one of America’s main strategic rivals was, quite literally, schooling the American president on economics and foreign policy.

A similar picture has emerged in Trump’s dealings with Congress. When the Freedom Caucus defied him on health care, the administration’s blustery threats against the dissenters came to nothing. House Republicans ignored his tantrum and continued their work. Now the president will likely be forced to endorse whatever they produce.

The same, no doubt, will be true of the construction of a physical barrier across the North American continent. Mexico has not been made to pay (and should not be). Trump has conceded that he will sign an omnibus spending bill that doesn’t include wall funding. In the long-term contest between Senate Minority Leader Charles E. Schumer (D-N.Y.) and the border wall, Schumer — armed with the Senate’s rules — is the safer bet. And the absence of that wall will be a lasting monument to Trump’s political impotence.

This is not a problem that can be solved by the big bang of the MOAB (nicknamed the Mother of All Bombs). In a number of cases, Trump has not been cunning but credulous; not an authoritarian but a pushover. During his campaign, Trump looked down on the weak; now, it turns out, he is weak.

Ultimately, Trump is failing because he has little knowledge of the world and no guiding star of moral principle. The best of our leaders — think Abraham Lincoln — have been sure about the truth and uncertain about themselves. Trump is the opposite. His mind is uncluttered by creeds. He knows what he wants at any given moment, but it can bear little relation to the moment following. Who really believes that he would be sleepless if the wall were not built or if NAFTA ultimately survived? Who believes he would not be sleepless because of a nasty joke at his expense during a dinner party?

Without deep and thoughtful beliefs, persuasion is impossible. It is public reasoning that allows others to follow a leader’s footsteps in the snow. What has Trump done to rationally and respectfully persuade his critics?

Without deep and thoughtful beliefs, the prevailing advice is often the latest advice. For a rootless leader, in Oscar Wilde’s phrase, “passions are quotations.”

Trump clearly wants to be judged by a frenetic level of activity. But the issue at hand is direction, not momentum. It is useful to undo some past liberal excesses, as Trump has done. But negation can’t be confused with inspiration. There can be no measure of political progress without a measuring stick of political conviction. Instead, we are treated to hysterical self-praise. Appalling — but, hey, what did we expect?

1 of 83 Full Screen Autoplay Close Skip Ad × A look at President Trump’s first 100 days View Photos The beginning of the president’s term has featured controversial executive orders and frequent conflicts with the media. Caption The beginning of the president’s term has featured controversial executive orders and frequent conflicts with the media. March 17, 2017 President Donald Trump, first lady Melania Trump and their son, Barron, walk to Marine One at the White House en route to Mar-a-Lago in Palm Beach, Fla. Jabin Botsford/The Washington Post Buy Photo Wait 1 second to continue.

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