Winners, when they reach the end zone, are supposed to act like they’ve been there before. So why is President Trump still waging war on Hillary Clinton? Why tweet about missing emails and ties to Ukraine when he’s the one inside the White House? Why send press secretary Sarah Huckabee Sanders before the cameras — nearly nine months after the election — to read what amounted to a multi-count indictment of Trump’s defeated foe?

In this, as he does so often, Trump serves as a magic decoder ring for our seemingly incomprehensible 21st-century politics. With reptilian clarity — hopeless on strategy, but instinctively keen — he seizes on the binary basics of our endless combat: To survive, one must have a foe.

Down deep, Trump surely knows he owes his presidency to Clinton. His vulnerabilities as a candidate were precisely the spots where Clinton was too weak to land a blow. The murkiness of his finances was offset by the shadiness of the Clinton Foundation. Her outrage at Trump’s boorish behavior rang false given her infinite tolerance for her husband’s. If Trump’s first impulse was always to dodge the truth, well, where had we seen that before? Clinton had to collapse in public before she was willing to admit to a mild case of pneumonia. Her story about her emails had more holes than Trump National Golf Club. As for the empty slogans of his campaign (“Build that wall”), they were hardly less substantial than hers (“Stronger together”). His ignorance of policy and history demanded a campaign about nothing. She gave it to him.

President Trump. (Jabin Botsford/The Washington Post)

So it happened that one of the most unpopular candidates in our history won his narrow victory. Voters in the key states of the electoral college disliked his opponent a little bit more.

Democrats looking ahead to 2018 might want to keep this history in mind. Approval ratings are a mirage. They ask the public to compare the president to some theoretical standard or ideal. Do you approve or disapprove of the way the president is doing his job? Compared to what? Lost in a desert of ballot-box ineptitude, the Democrats are crawling toward the false oasis of Trump’s low ratings — as though blind to the fact that Trump was never popular to begin with, and still he won.

Or rather, he survived the election, a feat managed by making it a series of head-to-head combats, against Low-Energy Jeb, then L’il Marco, then Lyin’ Ted and finally Crooked Hillary. Trump’s continuing focus on Clinton serves to remind all the people who held their noses while voting for him that elections aren’t about theoretical standards or ideals. They are about this one or that one. Too often, American voters feel like they’re dining at Hell’s Café, where the menu offers two dishes only: boiled work boots or roadkill tartare.

To win next year, Democrats will need to offer something more appetizing than the plate they served up in 2016. But their recently unveiled effort, called “A Better Deal,” ain’t it. While the nation is hurtling into the future, they’ve rolled out a recipe from the past, yet another “deal” to go with the Fair, New and Square deals of yesteryear. As for the vapid corporation-bashing at the core of the document, it feels like a ride in the DeLorean with Marty McFly, the timer on the Flux Capacitor set for 1901. What failed for William Jennings Bryan is unlikely to succeed today.

Behind the antique facade lay the same old policies. The $15-an-hour minimum wage, which may already be killing jobs where progressives have started adopting it. The $1 trillion infrastructure pledge that merely echoes Trump’s own pie-in-the-sky promise. The vague gesture of concern about rebuilding “rural America” — which Charles E. Schumer and Nancy Pelosi keep tabs on by jetting over it at 38,000 feet. And so on.

If America wanted this agenda, the Democrats would not be out of power from statehouse to White House. You can’t beat Trump by coining more vacuous slogans than his, or launching flimsier policy balloons. You can’t conquer his straw men with an army of your own. Trump’s opponents will only beat him with something new and better than the candidates, tactics and policies of the past.

These won’t be found in minority caucus rooms or the studios of MSNBC. To win a head-to-head against Trump, a party of tomorrow must turn its focus from Washington to the country — where it is going and how best to get there. Forget about Republicans. Forget, even, about Trump. Have an honest, hopeful conversation with America.

(Bastien Inzaurralde/The Washington Post)

He’ll never see it coming.

Read more from David Von Drehle’s archive.