If every member of the Senate looks into the mirror and sees a future president, then every president looks into that same mirror and sees himself on Mount Rushmore. Donald Trump, a mess of a man but brimming with self-regard, probably already sees himself up there with Washington, Jefferson, Teddy Roosevelt and Lincoln. It won't happen. Instead, he'd be lucky if he can get his face on a mug in the gift shop.

It just so happens that we have a gauge of what constitutes a great president. It was compiled years ago (1962) by the historian Arthur Schlesinger Sr., who surveyed 75 of his fellow historians on the subject of presidential greatness. They came up with eight categories. Suffice it to say that Trump whiffs every one, the last being the requirement that he "possessed a profound sense of history." Next president, please.

With Trump only in office for about one year, it's impossible to rate him on some of the other categories. For example, it's not yet clear if he's "held stage at a critical moment in American history" − although it is entirely possible that his very presidency is itself a critical moment. Still, it is clear that he will not measure up to the presidents the historian named as great − Abraham Lincoln, George Washington, Franklin D. Roosevelt, Woodrow Wilson and Thomas Jefferson.

More interesting to me is whether he will sink to the bottom. So far, just in terms of metrics and compared to some predecessors, he's not doing that bad. George W. Bush, a charming and utterly gracious man, was a catastrophic twofer. He took the U.S. to war in Iraq, a wrenching debacle: more than 4,000 Americans dead, nearly 32,000 wounded and the Middle East destabilized with Iranian influence enhanced. Then, too, Bush presided over a profound economic recession − not his decision, certainly, but Herbert Hoover didn't ask for the Depression, either.

Trump's numbers may turn out to be just as bad − or worse. But so far the economy is humming along, the stock market is soaring and a tax bill is on the horizon. Just in economic terms, nothing has happened yet to convince Trump voters that they made a mistake. In fact, some of the tonier ones -- modern day robber barons and such − are smugly satisfied. The president is doing what he can to destroy both bad and good regulations, the only exception being the ban on importing trophy elephant parts. It stands.

If any of that is good then it is more than offset by lots of bad. The U.S. is rudderless in world affairs. It stands alone in doing nothing to combat man-made climate change. It has withdrawn from or rebuffed trade agreements. It has a secretary of state who is hollowing out his department so that foreign diplomats, both at the United Nations and in Washington, wander the halls seeking someone with whom to do business. The remaining cabinet officers are similarly weakened or, perversely, determined to undo their predecessor's good work. It is a political autoimmune problem.

To fully understand how grandly Trump has failed as president, it is useful to see the thrilling new film about Winston Churchill, "Darkest Hour." It is set in 1940, in the days when Britain is deciding whether to sue for peace with Nazi Germany or continue a war it may badly lose. What was at stake, as Churchill recognized, was the very meaning of what it meant to be British. In two famous speeches, Churchill rallied his countrymen. As Edward R. Murrow once observed, Churchill "mobilized the English language and sent it into battle." It was, at the time, about the only weapon Britain had.

The contrast to Trump is stark. (Yes, I know, no one's a Churchill.) But Trump has made us a meaner, smaller people. He tweets the language of the school yard. It is full of resentment and bravado. He asks nothing of us. Instead, he validates meanness, opportunism and prejudice. Now, for instance, he asks us to disbelieve the many women who have accused Roy Moore of sexual harassment or what amounts to pedophilia. It is a squalid effort − just plain dirty.

There are no metrics to gauge this sort of thing. A moral gloom, as thick as a London fog of Churchill's time, has settled over America. It cannot be measured. Only names can be counted − the people who supported Trump and now the ones who say nothing. Moral principle has been replaced by political cowardice.

This is our darkest hour.

Richard Cohen's column is distributed by the Washington Post News Service.