This is the period when members of the herd of Democratic presidential candidates are testing various appeals to the party faithful. But the more serious contenders are also considering what attacks they might eventually employ against President Trump. The problem will come not in producing the list of potential vulnerabilities, but in narrowing it down.

My personal recommendation: relentlessly turning the president’s claim of authenticity against him, until his defining public attributes become national jokes. Every part of Trump’s appeal is fraudulent. His lies are not the filigree; they are the foundation.

The man who promised to drain the swamp imported alligators such as Paul Manafort and Michael Cohen. Trump himself tried to pull off a nine-figure real estate deal with proxies of Vladimir Putin while he was running for president .

The man who claimed he would bring business skills to the White House has cultivated a cloud of squabbling chaos around him. His management style — rewarding toadies and punishing honest disagreement — would push the average lemonade stand into early bankruptcy.

And, most disturbing, the president’s defiant nationalism is strangely lacking in basic patriotism. He is quick to question others’ loyalty — “Maybe you shouldn’t be in the country” — but remarkably slow to demonstrate loyalty of his own.

Recall that a month after the presidential election — when the extent of Russia’s assault on the U.S. electoral system was becoming clear — Trump’s transition team accused the U.S. intelligence community of making up the threat. “These are the same people,” they wrote, “that said Saddam Hussein had weapons of mass destruction.”

At that moment, I recall thinking for the first time: Trump and his team are willing to sell out the people defending our country for political reasons. They must have known that U.S. intelligence was accurate, and still they employed arguments favorable to Russian intelligence. It was unthinkable — until Trump forced us to think it.

Now, the Mueller report uses about 100 pages to detail all the contacts between Russia and Trump campaign officials. They could have rung the alarm on Russian information warfare at any point. But the Mueller report recounts not a single call to inform proper authorities. Instead, the Trump team anticipated and welcomed the practical assistance of a hostile foreign power. And they then tried to conceal that assistance in an escalating series of deceptions.

Amazingly, Trump’s campaign chairman provided a former Russian intelligence officer with polling data. Later, Russians with Kremlin connections promised dirt on Hillary Clinton. What transpired, in the judgment of special counsel Robert S. Mueller III, was not a criminal conspiracy. But not for want of trying.

Trump supporters must believe that deep down he is a true patriot. But the public evidence for this is scarce. It was certainly not evident during his nonexistent military career. It could not be proved by his casual slanders against the country. When told that “[Vladimir] Putin’s a killer,” Trump responded: “There are a lot of killers. . . . You think our country’s so innocent?” When asked about Turkish President Recep Tayyip Erdogan’s crackdown on dissent, Trump answered: “When the world looks at how bad the United States is, and then we go and talk about civil liberties, I don’t think we’re a very good messenger.”

Again and again, Trump is drawn toward the sheikhs, the generals and other despots. How does this comport with American ideals?

A political question remains. Will a Democratic presidential candidate be allowed to sound a certain trumpet of patriotism? For some on the left, even the word is tainted by militarism and racism. In a poll last year, 72 percent of Republicans called themselves “very patriotic.” Among Democrats, the figure was 29 percent. In some corners of academia, Trump’s right-wing identity politics is matched by left-wing identity politics, which finds the meaning of America in its defects.

Democratic political figures tend to identify with patriotism’s harder cases — flag-burning, or paying taxes or kneeling at a football game. This is admirable. But to properly call attention to Trump’s deficit of patriotism, Democratic candidates will need to say, without apology, that American ideals are a force for good in history, and that the United States is a force for good in the world.

For Americans, love of country entails a love of decency and human dignity. And it finds the meaning of America in its highest ideals.

I never imagined that the party of Ronald Reagan would cede the ground of patriotism. But in the Trump era, Democrats have a chance to seize it.

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